File Manager issues this message and fails to come up whenever the /tmp/.removable directory is owned by another user and is not in 1777 mode. This can happen, for example, when multiple users share a workstation.
Have the original owner use chmod(1) to change the mode of this file back to 1777, its default creation mode. Rebooting the workstation also resolves this problem.
This is a known problem that was fixed in the Solaris 2.4 release.