Error xxx: database disk image is malformed

[UltraUser]

Hello,

Back with a problem today.

I was trying to access one item in my huge UR database, a task actually, and this is the pop-up I got:
"Error loading item detail view: database disk image is malformed"

Hmmm... Well, I've tried a "compact and repair", which didn't end properly, because at some point it was interrupted with the same message (when at the 'compacting database' step):
"Error repairing database: database disk image is malformed"

Okay then. I've decided I could do without the offending item, so I deleted it. Or rather I tried because here's the message I got (you guessed it):
"Error deleting item(s): database disk image is malformed"

I don't have any other clue as of now. But this is a very annoying situation.
Kind people from UR, would you be so kind as to tell me what I can do?

Grazzie