PBEM Play-Altered Messages Show Up

[Strela]

Just got my first PBEM file from an opponant.  Two separate but similar messages pop up in my game window.  

First message says:

"scenario oob has been altered."

Second message says:

"Nation dat file has been altered."

Could someone in the know kindly tell me what this means?

Hi,

Are you both using the same version of the software?

You should both be patched up to version 1.02a.

David