The reason may be the new requirement of sending non-empty and non-zero (?) wpStarttime and wpEdittime parameters for all edit requests, including new page creations [1].
[1] http://svn.wikimedia.org/viewvc/mediawiki?view=rev&revision=42037
That would do it. It breaks even today's svn version of the python wikipedia framework.
Did anyone even think that this might break something?
I think you'd best revert that for a while; anyone using pybot is going to have to get re-synced, and anyone using any other page loader is going to have to modify their code. Is going to take a while. (yes, it would be good to convert to the API now that it is available; that will take even longer ;-)
Robert