I came across this problem on my own computer. When going to “Manage Wireless Networks” in the Network and Sharing Center, I saw icons for the wifi networks I had previously connected to, but the data in the columns was blank.

I did some googling and came across a couple of posts that had the fix and wanted to share it. Its quite simple. The file

C:\Users\Username\AppData\Local\Microsoft\Windows\UsrClass.dat

has to be removed. This is easy to do with the right tools.

Go to http://technet.microsoft.com/en-us/sysinternals/bb897556 and download the PendMoves and Movefile package. Copy the executable files to the C:\Windows\ folder.

Open an administrative command prompt.

Type in the following:

cd c:\Users\username\AppData\Local\Microsoft\Windows\

movefile UsrClass.dat “”

Now reboot the computer. The movefile program will delete the file on the next boot before it is in use by the system, and when it is found to be missing, it’ll be recreated. Customizations to the Notification Area will be lost, as will default program settings. Its a small price to pay for an actual fix to this quite annoying issue.

I had to troubleshoot a computer with Firefox 12. Firefox 3 ran fine. I cleared the profile in case that was corrupt, and it did nothing. It would start fine in safe mode.

After troubleshooting for a while I found the issue. Hardware Acceleration was turned on by default, which was causing Firefox to crash. Firefox (FF) worked fine in Safe Mode though, because Hardware Acceleration is OFF in Safe mode.

How to fix:

1) Start FF in Safe mode by holding down Shift while clicking the icon.
2) Go to Tools,  Options, Advanced, General.
3) Uncheck “Use hardware acceleration when available”
4) Click “OK” and restart Firefox normally.

This particular computer ran Windows XP, however the issue could crop up in any computer where there is a driver conflict of some sort that caused this.