hello RBCyr, because you've indicated that the problem started to happen after a windows system restore please first try a clean reinstall of firefox:

• download the full firefox setup file from https://www.mozilla.org/firefox/all/
• uninstall firefox on the machine
• manually delete all remaining files in the firefox program folder, which usually resides in C:\Program Files (x86)\Mozilla Firefox\
• reinstall firefox

in case this did not help, the xpcom error message at startup might also be caused by thrid-party security tools: http://kb.mozillazine.org/Browser_will_not_start_up#.22Couldn.27t_load_XPCOM.22_error

I've had the same problem and have read a couple of threads on here (one has since been archived) re-after downloading and installing various updates for Windows Vista....I noticed my Arial font looked funny, and so I attempted a system restore-it didn't work and caused my laptop to crash-some of my Windows files became corrupt; took it into a computer shop, they repaired Windows, and when I tried to click on my Mozilla Firefox icon, I got the above error message; I downloaded a fresh copy/version and my browser now works fine.

My 1,000,000,000 question is: which Windows Update caused my original problem?, i.e., the fonts to look funny? I don't want to install an update that is going to cause my fonts to go funny (that is what kicked this off to begin with) but I don't know which update it was: has anyone else noticed this when they installed new updates in Windows Vista? I installed the updates around 11th Feb. 2015. Many thanks!

This error is usually (or rather always) caused by other software that keeps a handle on files in the Firefox program folder and thus prevents the Firefox updater from updating all the file. This leaves you with a mixture of files that give you a not working Firefox installation. You need to do a clean reinstall to recover from this as posted above.

Hi,

Thanks for your reply. Are you suggesting that my font/appearance problem, post-a Windows Update was due to "other software that keeps a handle on files in the Firefox program folder and thus prevents the Firefox updater from updating all the file". I'm wanting to know which Windows Update caused my fonts/appearance to go funny, which then lead to a system restore, which then lead to my Firefox browser not working (the browser is fine no) but I still have updates that want to be downloaded and installed, yet I'm worried the same problem will occur if I install the updates. There are obviously Windows Updates that have caused my initial problem....the appearance/display to go funny, which is why I did a system restore in the first place.

My problem relates to this old thread, specifically the message by "spudtu": https://support.mozilla.org/en-US/questions/965228

-my problems started after I installed Windows Updates.

Thanks!

RBCyr said

I reset my computer to an earlier date. When I tried to connect to Foxfire after all I got was a box with the message "couldn't load XPCOM."

IS THAT GOING TO GET RID OF THE TAB HISTORY?????????????????

DO YOU CALL THAT A SOLUTION????????????? REALLY????????????????????

please stay in your own thread that you have opened about the issue & don't post in other threads if you have nothing constructive to add there. closing this one as the issue got already resolved for RBCyr...