Sometimes I've been able to get a drive that wouldn't validate from Workbench to do so on its own if I boot up with no startup-sequence. Just hold down both mouse buttons when rebooting to access the early boot menu, and select "Boot with no startup-sequence". If you use the "info" command from the initial Shell window, you can monitor the status of the validation process, normally it says "Validating" until the validation is complete.
If you eventually get an requestor with an error message regarding the partition, you might have to use something like Disksalv to try to repair/salvage your files, or just copy the data somewhere else and reformat the partition.
Hope that helps! :-)
