Hello Tone.

What's the bug number at bugzilla?

Assuming you mean something along the lines of:

XULrunner Error: Platform version '1.9.x.x' is not compatible

There are two possibilities, neither of which originate from Mozilla:

1. "You have some security software that was locking files in the Firefox program folder or have some kind of file protection active and thus prevented the updater from replacing them." quoted from another thread. The solution is to just download the full installer from http://getfirefox.com and run it, you will not lose any user data like bookmarks or settings.

2. You have Malware locking files in the same way. The solution is to battle it out for weeks with said malware until you give up and run http://wubi-installer.org

No, I meant the bug number at Bugzilla. This one's, for example, is 531675. Since you said "fix the XULRunner bug", I assumed it's a known bug that's being worked on...

Such errors are usually caused by files in the program folder being locked or protected by security software. This will prevent the updater from updating all the files to the new version. If files are locked then there is nothing that Firefox can do about it and you need to configure your security software properly. You may find files with something like moz-backup in the name.

You usually need to delete the Firefox program folder and do a clean reinstall to get all files up to date.

If you are using Zonealarm, try turning off virtualization (Browser Security; Settings; Advanced)when you do the reinstallation of Firefox. I couldn't get past this error until I tried that.