The first error/backtrace seems like a corrupt file. Good thing you purged and reinstalled.
Yes, very weird.
Second one is rather common. Try raising the debuglevel in the config file to 9, so that more detailed information will output to the log.
Yes, well, unfortunately, I did that. I mentioned it in the first post:
Enabled level 9 logging.
Those lines were in the level 9 debugging log. Not really informative.
The only thing that comes to mind is whether I could somehow turn on debugging (more debugging than the logs) supposing I’d actually download the source files and configure the compiling with a switch like “–enable-debug”. Is this possible (i.e. is there such a compiling switch)? Because the quotes in yesterday’s post came from a “stock” install from the Ubuntu repositories.