Are your workspace and project files (.vpw and .vpj) stored in the VOB? If so, then I think you will need to use a separate config for when you are not attached to Clearcase, as you have already suggested. Since you aren't connected to Clearcase, you wouldn't be working on the same set of files, so creating a different workspace for that seems like the right thing to do. You can put a shortcut icon on your desktop for each different config.
If your workspace and project files are stored locally, which is something we highly recommend, then you may be able to avoid this by changing the Auto Restore settings. Select Tools > Options > Application Options > Auto Restore and change the following to "False": Auto restore files, Auto restore, workspace files, Auto restore working directory.