The few answers found on the Apple Discussions seemed to focus on permission issues, but I didn't see any reported successes in response to suggestions to fix permissions — which may or may not mean anything one way or the other. With that as a starting point, I would try running Permission Repair as a first pass attempt at a fix. However the fact this is occurring on more than one volume would tend to eliminate that as a problem source. Still it cannot hurt.
If that fails, in an attempt to narrow the solution space, I would resort to the standard troubleshooting step of booting from a clean test account and see if Erase Free Space works from there.
