I had a problem where Thunderbird had this error “Software Update Failed – One or more files could not be updated” and kept looping until you cancel the update. Turned out to be Logitech Quickcam! If you have the same problem, try this:
If you use a Logitech Web camera, the QuickCam software can interfere with Firefox updates. Physically disconnect the camera from your computer. If you have a QuickCam icon in the Windows system tray, right-click the icon and select “Exit”.
If you do not see a QuickCam icon, you stop the software from running using Windows Task Manager, as follows:
- Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Alt+Delete). The Windows Task Manager will open.
- Click the Processes tab.
- Select the “Quickcam.exe” entry in the processes list and click
- Click in the Task Manager Warning dialog.
With Quickcam no longer running, try updating Firefox again by clicking the Help menu, and selecting Check for Updates….
Worked for me. Try this link for other options: