Botched block in the DB. Usually rebuilding the Armory DB is enough. Worst case scenario you'll have to delete your copy of the blockchain and redownload it
Why doesn't this worst case scenario excite me at all? Thing is like 30 gig.
I have to say that this bug has been there from the very beginning and somehow it's still not mitigated in any way. Reference bitcoin client has no issues with it, but somehow armory cannot handle it. Why? I call it bs.
It's very sad how otherwise functional client suffers from such usability problems.