Player 1 Obat file different or corrupt

[Mobhack]

Then your opponent (who is player 1 as he set up the PBEM) most likely has different OOB files from yours. Either he is on a different version of the game, or has edited his oobs in mobhack (or you have) (or you both have!), or has downloaded an altered version of the oob in question (or you (or both of you) have).

You'll need to speak to him about this, assuming that you have not yourself edited or altered your own OOB files.

Cheers
Andy