Bart’s Blog

If you need to remove sync partnerships with systems that are no longer available, or if you want to recover from a corrupt CSC cache then you can use the following procedure to re-initialize the offline cache.

1. Locate the following registry key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CSC
2. Point to New, and then click Key.
3. Type Parameters in the box.
4. Right-click Parameters, point to New, and then click DWORD (32-bit)Value.
5. Type FormatDatabase, and then press ENTER.
6. Right-click FormatDatabase, and then click Modify.
7. In the Value data box, type 1, and then click OK.
8. Exit Registry Editor, and then restart the computer

http://support.microsoft.com/kb/942974