Pdf forms in Adobe Reader are looking different than they used to. I also keep getting a message at the top which says "This pdf document might not be displayed correctly." But the biggest problem in documents that I was able to fill in information online previously are not working. In particular the tax form 941 which I need to send in!!! Help!
It looks that you are currently using the build-in Firefox PDF reader and that build-in PDF reader can't be used to fill a PDF form, so you will have to make sure that the Adobe Reader is installed properly.
You can try to disable this PDFjs reader and set the pdfjs.disabled to true on the about:config page.
I'm not seeing the Abode Reader plugin in your system details list.
Is that plugin disabled (Tools > Add-ons > Plugins) ?
Try to delete the pluginreg.dat file in the Firefox Profile Folder and maybe addons.sqlite as well to reset the plugin registry databases.
Note that you are currently running a Firefox 19 beta version, no you may need to create a new profile or try the current Firefox 18.0.2 release.