When starting my MacBook Pro this morning, Eclipse says:
Workspace in use or cannot be created, choose a different one
and Netbeans says:
The Source folder /Volumes/data/domains/... cannot be restored.
I have deleted the .lock file out of my metadata directory in the eclipse workspace, and afterwards restarted the computer, but still have the problem:

In finder I can navigate to the workspaces no problem, those volumes are connected.
I am quite certain I didn't have Eclipse and Netbeans open when I closed the computer as I am aware that it causes these problems.
In configuration/.settings/org.eclipse.ui.ide.prefs I tried changing the RECENT_WORKSPACES entry but this didn't have any effect.
How can I get Eclipse and Netbeans to recognize their workspaces again?

ls /Volumes? Have you tried selecting the workspace when prompted to do so in Eclipse (I have no experience using Netbeans)? – Daniel Beck Dec 6 '10 at 16:31