It happens maybe once a month. Plugins = Addons Auto-Mark Pair-Tag-Highlighter Spell-Check Tree-Browser (so no...in theory)
All instances have their own configs. If I say rename the offending config to config.old and restart it will be fine. If I then rename the config to be used the problem returns, until you restart geany over and over.
Devils pie is ancient heh no I don't use it.