Have you tried:
– checking through Troubleshooting WordPress 3.1 – Master List
– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).
– switching to the Twenty Ten theme to rule out any theme-specific problems.
– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.
Thanks! I will give it all a shot!