Fresh install of 1.2.5 Server on Linux seems to have out-of-sync versions of mods compared to the 1.2.5 client fresh install on Windows (if it matters) and won't connect. Also tried a linux client.. same error.
ForgeMultipart (1.0.0.219 server, 1.0.0.227 client)
McMultipart (1.0.0.219 server, I don't see a file with this name on the client)
Did the client config get updated after the last changes to 1.2.5?