Just experienced 4 crashes in a row... the first one was silent though the other 3 displayed the "illegal operation" thing. I was tagging using tre Action Window Tag Info feature when all the crashes happened.
[EDIT] As a test, I've been tagging around 35 new albums this evening using only view schemes and the main display area for that. Not a single crash. For the last album, I've switched to tagging it with the Action Window... MC has crashed. The crash normally happens after entering the data for a tag and clicking the "tab" key to validate the change.
Hope it helps.