simonesch said

. . . as long I will not log off and log on again

Log on/off of what?

In the address bar, type about:crashes<enter>. Note: If any reports do not have BP- in front of the numbers/letters, click it to submit them.

The crash report is several pages of data. We need the report numbers to see the whole report.

Using your mouse, mark the most recent 7 - 10 Submitted crash reports, and copy them. Now go to the reply box and paste them in.

For more help on crash reports, see; https://support.mozilla.org/en-US/kb/firefox-crashes-asking-support

Hello FredMcD, thanks for your comment. Unfortunately I have no crash report. about:crashes shows nothing, no report.

Okay. When you open the browser, what happens? Does the window open then close? Does the icon show up on the computer's taskbar?

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

The windows opens for a split second, you can just see the frame and then it disappears. The content (e.g. start page) isn't visible as the windows disapears too fast. Same when starting in safe mode, no difference to a normal start.

Regards, Simon

Okay. Let's try this first:

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

Hello FredMcD, thanks for the idea, but I was unsuccessful. I removed all the Mozilla Firefox lines in my Kaspersky Internet Security Firewall and tried it again. Same behaviour. First start: Firefox starts for less than a second and closes immediately. -> Klick again on the icon -> Firefox starts perfect and runs stable. I updated today to Firefox 66.0.2 and my Kaspersky Internet Security is also up to date. Even when I disable Kaspersky I have the same effect. Regards, Simon

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

Did you check the Windows Event log to see if there are details in that log?

Same result when I start my computer in safe mode with network support. BUT: When I log in and start Microsoft Edge first (starts perfect) and after Edge I start Firefox, it doesn't crash.

I have tested different secure and serious start pages, this makes no difference.

The Windows Event log has nothing logged about that.

Hear's hoping you don't have this:

You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

Thanks again for your ideas. But no news. I tried out all of the security/malware scanners. They found nothing except some tracking cookies. The problem still exists.

Kind regards, Simon

It is possible that there are multiple versions of one or more DLL files and that Firefox tries to use an incompatible version that causes a crash. If Edge start a compatible DLL then Windows uses this version instead of the version that Firefox seems to be trying to use.

I don't know if you can check this with a Sysinternal tool.

• https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer

OK! I'm not familiar with the process explorer, how can I log/see which dlls are loaded when Firefox starts?