Army Group South problem -- help

[yooper]

I'm still seeking help for the following problem: I'm in the third or fourth Pripyet Marsh scenario. The one where your assaulting a collective or a small city in the north protected by numerous anti-tank guns, field pieces and BT-5s.

Six or seven turns in -- in the middle of a turn -- the game switches to 2-player mode and won't let me continue. A little clock appears in the bottom right corner and counts down to zero, then starts over.

I really want to finish this game. Any suggestions????