I think it wont be to wise solution with WSE and all... Just saying... We didn't have WSE last time I guess..
It tests checksum of warband executable (at least it says so).
If thats happening, you should use an older mb_warband.exe.
But in that case, maybe it's really easier just downloading the standalone client
from taleworlds' site.
Anyway, I cease playing until these lazy bastards fix this issue
I don't have enough free space to install anything else