I’ve been seeing several forum members on Go Firefox! getting the error: Unexpected installation error -203 When attempting to install extensions and/or themes. In most cases these members have recently upgraded from Firefox 2 to Firefox 3 on the same profile. This error message can be caused by either: security software, which may be preventing these files from being updated corrupted configuration files on your computer 99% of the time it is going to be caused by corrupted configuration files on your computer. To fix this problem follow these steps: Close Firefox Locate your Profile Folder Delete the following files…