Ok, so I was playing this guy yesterday. During the game, sort of at the midgame point, he took a pawn with his knight, but then the board changed completely, his knight hadn't taken my pawn and moved to another square attacking my queen. What's weirder, he ended up with 3 knights. When I used the bishop to trade one, the knight disappeared. 

It was pretty weird. 

http://www.chess.com/livechess/game.html?id=8651738

this? can't see anything strange here

well, some moves maybe ;) but nothing "illegal"

dont know if cheating is possible

It's when I moved the bishop to an empty space, the board I saw was different from the one recorded which I had checked. When I moved that bishop on move 19, there was a Knight on c3. And before that as well, I saw different board than the one recorded.

It sounds like it might have been a screen redraw issue on your side.  He moved the knight but the square it vacated also had a knight on it after he'd moved -- am I understanding correctly?  If so, you could probably have fixed it by minimizing/maximizing your screen.  As for your opponent's comments after the game he was probably just messing with you.  I very seriously doubt there's any way your opponnet could have caused this to occur deliberately.

ChessMastora which browser are you using ?

To: TheGrobe, yes that's exactly right, the place his knight vacated was then occupied by another knight but only I think a 2-move later. And then the capture stuff got messed up. He seemed to have seen it as well since he commented first, saying I was 'lying' or sth. But if you have encountered the problem before, it probably is my problem. Thanks.  I shall delete this thread in a days time unless there should be any posts from another perspective. 

Kohai, I'm using Google Chrome, it is OK? I never had a big problem with live chess before on this, so I think it's OK.

To the Grobe again, actually I just replayed the game on record, the 'new' knight wasn't on the square his knight vacated, it was on a square his knight could have moved t. if you go to http://www.chess.com/livechess/game.html?id=8651738 and see where I moved my bishop to empty space, that's where his 'new' knight was. 

chessMastora,

I had a game where my opponent's move left his piece on the square and moved it to a new square.  I captured it with screenshots - showing both an unmoved knight and a knight that moved.   at the same time, when I moved my queen it disappeared....   fortunately, I was able to checkmate him in 7 moves, despite the fact that by then, he had 4 knights and two queens showing, while I have only my king and a few pawns still showing.  (my pieces apparently still existed, but were not visible to me any longer, I had to remember where I put them....)

    I got the end position in a screenshot too, and sent that to Erik in email so he could look at it and ponder the fact that, although the moves showed correctly in the moves list, the board was quite "hosed up."

   have not experienced similar since upgrading to windows 7, 64 bit, and on a newer edition of firefox.

but yes, it was weird and disconcerting when it happened.

the live chess was acting weird for me yesterday too. everything was going fine, but then my pawn was taken by a piece that wasnt there... then it happened to my opponent when he dropped 2 pieces. we were both really confused

Thanks RetGuvvie and maul for sharing that similar experience. I might be seriously mistaken here. 

I am certain it was a software glitch and you owe your opponent an apology.

I figured that was the case... that it was some type of image glitch. When I move a piece and lose connection around the same time, the chess board/screen freezes with a piece in both squares . It doesn't happen often but when it does I immediately know there's something wrong. (happens on yahoo chess much more frequently)

I have seen some wierd things like this too.  It has been a while though.

I was playing live chess yesterday but nothing weird happened.

Why didn't you do a rematch, and see how he did it?

Four knights, two queens and invisible pieces? That sounds like a fun game!

This is how the legend of the phantom knight got started.