What if in Websphere Studio Application Developer you have set a workspace as default and now you want to change it?
Setting a workspace as default make WSAD not asking you for which workspace to use. If you have to reset the option execute WSAD from command line with the -setworkspace parameter.
On windows systems the location probably is the following
C:\Program Files\IBM\WebSphere Studio\Application Developer\v5.1.1>wsappdev.exe -setworkspace
Maybe this could even work for pure eclipse but I’ve not tested it.