When playing the game chess, is there any way to move a pawn if say?

That was definitely an illegal move, the only way a pawn can get out of that type of "stalemate" is by moving sideways to capture something.

It has to capture to move diagonally.

There is a secret pawn move called en passant where the pawn captures another pawn that ran by it using 2 steps from an opening move. In that case the en passant pawn moves diagonally behind the running pawn and captures it, so it's still technically a capture.

Thats an illegal move. Pawns can only move diagonal while directly taking an opponents piece or while performing 'En passant'. But 'En passant' does not take place while the two pawns are directly infront of one another.

"En Passant" is not a secret pawn move. It's a perfectly legal rule, and anyone can apply it under certain circumstances.

But in your case, it sounds like it may have just been a glitch in the program...that's not good, of course.

Pawns capture by moving one space diagonally.

Oh, Yahoo has screwed up again. I use http://www.freechess.org/

Yahoo's Chess system does that now and again. You aren't the first to complain of such.