You're right "--fix-protocol" fixes cgminer too.

Funny thing, cause 2.9.3 was working fine the last 3 days.
I use p2pool, but apparently Bitminter and Eligius (which both use GBT) in my backup pools can trigger the bug since this morning even if they aren't used.
Posted a backtrace to #cgminer, hopefully it will help debug the problem.
If you mine in p2pool use another p2pool node as backup. There is few public nodes open for everyone.