Illegal Move

I was playing chess against a computer today (not on this site just a computer version) and the computer made a move I thought it couldn't. I had my Queen on A5 and his King was on D8 giving me a diagnal attack on him which was blocked by his Rook on C7. He moved his Rook to C1 which checked my King but left his wide open to my Queen. My question: Is it a legal move if it checks the enemy King but leaves yours open to attack?

I would assume the computer would have those rules programed in but I wanted to double check to see if that was a common rule or not.

Lol, no, his rook was pinned to his king.

Sounds like some kind of transmission error, i.e. player and computer were looking at different positions?

That's what I thought, considering some of the other oddities of this version of chess I'm assuming it's just not a good program