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}

Hi FredMcD, thanks for your suggestions. I tried removing Firefox from McAfee's firewall list (for some reason it was in the list twice), but still no luck. I also followed the instructions in the link you supplied re. setting Firefox's incoming and outgoing permissions to "open to all devices", but that didn't work either :(

In case anyone comes across this later, it was Firefox 71 that seems to be the culprit. I rolled back to Firefox 70.0.1 and that works perfectly. No idea why Firefox 71 was so broken for me.

alexblake2 said

In case anyone comes across this later, it was Firefox 71 that seems to be the culprit. I rolled back to Firefox 70.0.1 and that works perfectly. No idea why Firefox 71 was so broken for me.

I have the same exact problem. 70.0.1 Ok 71 doesn't start

I tried a fresh install after completely uninstalled the previous version and doesn't start.

Can i ask you what is your CPU?

Hi

My CPU is an i7 6700K.

Did you try using something like Revo Uninstaller? I was recommended to try that so that it clears out any lingering registry entries. In the end I didn't need to, as 70.0.1 works fine for me.

If I were you I'd stick with 70 for now and see if there's an update to 71 to fix this issue.

hi, the symptoms sound very similar to https://bugzilla.mozilla.org/show_bug.cgi?id=1590430 - did you ever use comdo security products in the past or even if not, could you check if there's a file called IseGuard64.dll, IseGuard32.dll or similar located under C:\Windows\system32\ or your system drive?

philipp said

hi, the symptoms sound very similar to https://bugzilla.mozilla.org/show_bug.cgi?id=1590430 - did you ever use comdo security products in the past or even if not, could you check if there's a file called IseGuard64.dll, IseGuard32.dll or similar located under C:\Windows\system32\ or your system drive?

Ok problem resolved Thank you

philipp said

hi, the symptoms sound very similar to https://bugzilla.mozilla.org/show_bug.cgi?id=1590430 - did you ever use comdo security products in the past or even if not, could you check if there's a file called IseGuard64.dll, IseGuard32.dll or similar located under C:\Windows\system32\ or your system drive?

Turns out there's iseguard64.dll in my System32 folder. Last modified two years ago, don't know where it came from through as I've not used Comodo products for many years. Can this file be safely deleted?

yes, please remove it - afterwards firefox will hopefully be back in working order.

Thanks, that seems to have fixed it! I really appreciate the help.

you're very welcome, i'm glad that you have back your firefox :))