Unable to start the workbench?
In some problematic situations (e.g. if a user has ran out of disk space) then a file or files in the workspace sub-folder ".metadata" can get corrupted and Workbench may not start up correctly when you restart Altair SLC.
By pointing to a different workspace this can help verify that there is something wrong with the old .metadata directory. The .metadata directory holds cached information, local history, saved dialog box positions and that kind of thing. The source code in the projects will still be ok.
To fix it the simplest solution is to rename .metadata in the corrupt workspace to something else. Re-start Altair Analytics Workbench and point to the existing workspace folder. Altair Analytics Workbench should start but there will initially be an empty list of projects in the Project Explorer. (Note that you may need to select the folder option to show hidden files and folders in order to see this .metadata folder.)
Note that your projects and source code stay exactly where they used to be. Restoring the list of projects and source code files is purely a metadata regeneration exercise. To rebuild the metadata you need to import the existing projects by going to File->Import->General and highlight Existing Projects into Workspace click Next and then Browse to the problem workspace. You should see a list of your projects appear already pre-selected. Select Finish and the metadata should be re-generated. Your projects and source code should re-appear in the Project Explorer and you are good to go again.
Please give this method a try and let us know if it is successful in fixing the problem.