This article covers a Firefox crash that affects Windows XP users when they start Firefox. The problem is caused by malicious software (also known as malware) and is not caused by Firefox itself. It appears to affect users in several countries but has mainly been seen in Russia.
We are still investigating the issue, but several users have reported that the following instructions solve the problem with Firefox crashing:
Open Regedit: Click the Windows Start button, and select Run.... Type in regedit and click OK.
Locate the registry key: HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows NT \ CurrentVersion \ Winlogon.
Find the entry called Userinit. Normally, it should only have the value of C:\WINDOWS\system32\userinit.exe. If there is a comma and more text after it, this might be malware. Remember the part after the comma, which might look like this: C:\WINDOWS\system32\3abcde04.exe.
Open My Computer and navigate to the folder containing the malware file. In the example above, this is C:\Windows\system32.
Locate and then remove the malware file by selecting it (3abcde04.exe in the example above) and pressing the Delete key while holding down the Shift key.
Go back to regedit, right-click on Userinit and select Modify...
Remove the part of the entry Userinit so it only includes C:\WINDOWS\system32\userinit.exe and click OK.