Solve this problem with these steps:
- Verify that you can update using TortoiseSVN (this will guarantee that your .svn is not corrupt)
- Delete all your projects that have this problem, but in the delete dialog, do not delete the project contents!
- Select File -> Import -> Existing projects into Workspace.
- Select your projects folder or your workspace folder.
Subeclipse should now detect and connect your projects automatically, without need to select ‘Share Project’ for each one of them.