There is some command somewhere that is causing a dump so deep that there's very little information (other than that there was a dump) being generated. (A deadlock among DDL and parse locks is detected.)
I don't know if something I did so long ago which I don't remember is now rising up and causing issues, or if some Oracle designer had the same sort of misspent youth as I did.
Part of the dump indicates:
11/23/2010 ETA: Googling found me a page which indicated:
(Updated 19.11.2010) For some components the action is set to ‘xyzzy’. This seems to be a default value set when the component is opened, but before any of the pages are processed.
So it was an Oracle designer, and not me being clumsy.