@Richard: I have no history with the extension so I could be way off with assumptions; just for giggles, try to launch the manager app with root privileges:
sudo boincmgr
It probably is unrelated due to the type of error reported, but there's always that 0.0003% of a chance.
Normally, IOp Errors happen when they're trying to do something they're not allowed to do or the direction they're trying to take doesn't exist. (Laymen's terms at least!) As such, there's a good chance one or more of the many, many, many dependencies may in fact be too "new" where functions that used to exist simply don't exist or they have been changed and now act differently, or, with that fraction of a percent chance, they may now have elevated privileges today where they didn't back then, so the "sudo" above should cross that option off.