I was never able to reproduce this, nor was Gary (Pidgin lead developer).
Are you able to narrow this down at all? For example, if you run:
mkdir pidgin-test
pidgin -c pidgin-test
that will start with a blank config. Does it happen then? If not, try
adding accounts and/or enabling plugins until you reproduce it.
Or, alternatively, work from the opposite direction by copying your config:
cp -a ~/.purple pidgin-test2
pidgin -c pidgin-test2
That should reproduce it. Then remove things from your config until it
stops.
Or, do both and diff the two configs to know what to tweak.
--
Richard