hello, what security software are you using (if any)?

please also go to the firefox menu ≡ > help ? > troubleshooting information, copy the contents of that page and paste them here into a reply on the forum? this might give us a clue what is going on...

I'm on a mac and I'm not currently using security software.

{

 "application": {
   "name": "Firefox",
   "version": "45.0.1",
   "buildID": "20160315153207",
   "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Firefox/45.0",
   "safeMode": false,
   "updateChannel": "release",
   "supportURL": "https://support.mozilla.org/1/firefox/45.0.1/Darwin/en-US/",
   "numTotalWindows": 1,
   "numRemoteWindows": 0,
   "remoteAutoStart": false
 },
 "modifiedPreferences": {
   "accessibility.typeaheadfind.flashBar": 0,
   "browser.cache.disk.smart_size.first_run": false,
   "browser.cache.disk.hashstats_reported": 1,
   "browser.cache.frecency_experiment": 2,
   "browser.cache.disk.capacity": 358400,
   "browser.cache.disk.smart_size.use_old_max": false,
   "browser.cache.disk.filesystem_reported": 1,
   "browser.download.importedFromSqlite": true,
   "browser.places.smartBookmarksVersion": 7,
   "browser.search.suggest.enabled": false,
   "browser.sessionstore.upgradeBackup.latestBuildID": "20160315153207",
   "browser.startup.homepage_override.mstone": "45.0.1",
   "browser.startup.homepage": "http://my.xfinity.com/?cid=xfinityconnecttocomcastnet#8",
   "browser.startup.homepage_override.buildID": "20160315153207",
   "browser.tabs.warnOnClose": false,
   "browser.tabs.loadInBackground": false,
   "browser.urlbar.default.behavior": 0,
   "dom.apps.reset-permissions": true,
   "dom.mozApps.used": true,
   "extensions.lastAppVersion": "45.0.1",
   "font.language.group": "x-western",
   "font.internaluseonly.changed": true,
   "gfx.crash-guard.glcontext.deviceID": "0x11a3",
   "gfx.crash-guard.glcontext.appVersion": "45.0.1",
   "gfx.crash-guard.status.glcontext": 2,
   "media.gmp-gmpopenh264.lastUpdate": 1454954503,
   "media.gmp-gmpopenh264.version": "1.5.3",
   "media.gmp-manager.lastCheck": 1458822815,
   "media.gmp-gmpopenh264.abi": "x86_64-gcc3-u-i386-x86_64",
   "media.gmp-manager.buildID": "20160315153207",
   "network.predictor.cleaned-up": true,
   "network.cookie.prefsMigrated": true,
   "places.history.expiration.transient_current_max_pages": 104858,
   "places.database.lastMaintenance": 1458397227,
   "plugin.importedState": true,
   "plugin.disable_full_page_plugin_for_types": "application/pdf",
   "print.print_resolution": -437918235,
   "print.print_paper_width": "  8.50",
   "print.print_paper_size_unit": 0,
   "print.print_to_file": false,
   "print.print_footerright": "",
   "print.print_footerleft": "",
   "print.print_orientation": 0,
   "print.print_headerright": "",
   "print.print_margin_top": "0.5",
   "print.print_paper_height": " 11.00",
   "print.print_scaling": "  1.00",
   "print.print_unwriteable_margin_right": 13,
   "print.print_reversed": false,
   "print.print_unwriteable_margin_left": 13,
   "print.print_paper_data": 0,
   "print.print_unwriteable_margin_bottom": 59,
   "print.print_paper_name": "",
   "print.print_headerleft": "",
   "print.print_oddpages": true,
   "print.print_bgimages": false,
   "print.print_duplex": -437918235,
   "print.print_evenpages": true,
   "print.print_margin_left": "0.5",
   "print.print_shrink_to_fit": true,
   "print.print_margin_right": "0.5",
   "print.print_unwriteable_margin_top": 59,
   "print.print_bgcolor": false,
   "print.print_margin_bottom": "0.5",
   "print.print_in_color": true,
   "print.print_paper_size_type": 1,
   "print.print_page_delay": 50,
   "privacy.sanitize.timeSpan": 0,
   "privacy.sanitize.migrateClearSavedPwdsOnExit": true,
   "privacy.cpd.sessions": false,
   "privacy.cpd.cookies": false,
   "privacy.donottrackheader.value": 1,
   "privacy.clearOnShutdown.passwords": false,
   "privacy.cpd.formdata": false,
   "privacy.sanitize.migrateFx3Prefs": true,
   "security.tls.insecure_fallback_hosts": "paypal.com",
   "security.ssl.enable_ocsp_stapling": false,
   "security.tls.version.max": 1,
   "security.disable_button.openCertManager": false,
   "services.sync.declinedEngines": "",
   "services.sync.lastPing": 1458832313,
   "services.sync.lastSync": "Thu Mar 24 2016 09:21:55 GMT-0600 (MDT)",
   "services.sync.numClients": 4,
   "services.sync.engine.prefs.modified": false,
   "storage.vacuum.last.index": 1,
   "storage.vacuum.last.places.sqlite": 1457563044
 },
 "lockedPreferences": {},
 "graphics": {
   "numTotalWindows": 1,
   "numAcceleratedWindows": 1,
   "windowLayerManagerType": "OpenGL",
   "windowLayerManagerRemote": true,
   "supportsHardwareH264": "No; ",
   "adapterDescription": "",
   "adapterVendorID": "0x10de",
   "adapterDeviceID": "0x11a3",
   "adapterRAM": "",
   "adapterDrivers": "",
   "driverVersion": "",
   "driverDate": "",
   "webglRenderer": "NVIDIA Corporation -- NVIDIA GeForce GTX 680MX OpenGL Engine",
   "info": {
     "AzureCanvasBackend": "skia",
     "AzureSkiaAccelerated": 1,
     "AzureFallbackCanvasBackend": "none",
     "AzureContentBackend": "quartz"
   }
 },
 "javaScript": {
   "incrementalGCEnabled": true
 },
 "accessibility": {
   "isActive": false,
   "forceDisabled": 0
 },
 "libraryVersions": {
   "NSPR": {
     "minVersion": "4.12",
     "version": "4.12"
   },
   "NSS": {
     "minVersion": "3.21.1 Basic ECC",
     "version": "3.21.1 Basic ECC"
   },
   "NSSUTIL": {
     "minVersion": "3.21.1",
     "version": "3.21.1"
   },
   "NSSSSL": {
     "minVersion": "3.21.1 Basic ECC",
     "version": "3.21.1 Basic ECC"
   },
   "NSSSMIME": {
     "minVersion": "3.21.1 Basic ECC",
     "version": "3.21.1 Basic ECC"
   }
 },
 "userJS": {
   "exists": false
 },
 "crashes": {
   "submitted": [],
   "pending": 0
 },
 "extensions": [
   {
     "name": "BuiltWith",
     "version": "1.9.6.1-signed",
     "isActive": true,
     "id": "gary@builtwith.com"
   },
   {
     "name": "ColorZilla",
     "version": "2.8.2",
     "isActive": true,
     "id": "{6AC85730-7D0F-4de0-B3FA-21142DD85326}"
   },
   {
     "name": "DNS Flusher",
     "version": "4.0.0",
     "isActive": true,
     "id": "{7d575baa-b543-11dc-8314-0800200c9a66}"
   },
   {
     "name": "Firebug",
     "version": "2.0.15",
     "isActive": true,
     "id": "firebug@software.joehewitt.com"
   },
   {
     "name": "Firefox Hello Beta",
     "version": "0.1",
     "isActive": true,
     "id": "loop@mozilla.org"
   },
   {
     "name": "IP Address and Domain Information",
     "version": "2.0.4",
     "isActive": true,
     "id": "jid0-jJRRRBMgoShUhb07IvnxTBAl29w@jetpack"
   },
   {
     "name": "PageRank",
     "version": "2.0.1-signed",
     "isActive": true,
     "id": "PageRank@addonfactory.in"
   },
   {
     "name": "RoboForm Toolbar",
     "version": "7.9.16.9",
     "isActive": true,
     "id": "{22119944-ED35-4ab1-910B-E619EA06A115}"
   },
   {
     "name": "Snagit Autoscroll Helper",
     "version": "1.9.7.1-signed",
     "isActive": true,
     "id": "autoscrollhelper@techsmith.com"
   },
   {
     "name": "Wappalyzer",
     "version": "3.2.2",
     "isActive": true,
     "id": "wappalyzer@crunchlabz.com"
   },
   {
     "name": "Adobe Acrobat - Create PDF",
     "version": "1.1",
     "isActive": false,
     "id": "web2pdfextension@web2pdf.adobedotcom"
   }
 ],
 "experiments": []

}

please enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for bold preferences starting with security. - right-click and reset those entries to their default values.

Thank you, that worked. Not sure how they were set to user set but are now back to default.