After a major update last night boincmgr could not find its project list.

Lots of nvidia updates and I thought it was another nvidia botch
so removed nvidia to go to nouveau drivers then reinstalled nvidia
(some reboots along the way).
Which did not help.

syslog showed:
do_IRQ: 18.34 No irq handler for vector

I have had apcusbd running all along to track power events.
From a hint on the net about apcusbd and this sort of thing I did
sudo service apcusbd stop
and now boinc finds the project again.

So the problem vanishes with this change. SOLVED, sort of.
Posting this here in case it might help someone.