From what you've said, I believe the problem is with your saved game so reinstalling might not be required...
But if you want to give it a go there are just a few steps to consider.
1. Move any folders containing any graphics/skins/etc. that you may have added to your game to a safe place on your computer.
2. From the add/remove list found in 'Control Panel', remove Football Manger 2008.
3. Delete the folder called 'Sports Interactive' located in 'Application Data' which is usually found here >>
C

Documents and Settings\(your name)\Application Data
This folder may be hidden.
4. Delete the 'Sports Interactive' folder from your 'My Documents' folder.
5. (Optional but recommended) Run a registry cleanup program such as CCleaner >>
http://www.ccleaner.com/download
6. Reboot
And you're done