My PBEM opponents are getting this with RC5:
I thought it might be a problem with different versions (I thought we were all on RC4), but when I updated to RC6 I had the same problem. Reverting to RC4 fixed it for me.
I also noticed the font for the combat power values of Union forces on the map was large, white and probably couldn't handle five digits without overrunning the borders of the counters. I was in a hurry to repair my game and get another turn out, so I don't have a screenshot of it. This is at 1920X1200 resolution.
I'll update this if my opponents revert to RC4.