Sounds like your opponent had a way of leveraging a bug to his advantage, or else he might have been just been hammering the "offer-takeback" button in the hope you would resign. The fact that you went back several moves gives a lot of weight to this idea.
You did the right thing, you were only guesting after all and he knows you had the better of him.
A related story: FICS does not have time-lag detection like chess.com, or at least the support does not work in linux. You are expected to download software called "Timeseal" if you are a linux user, otherwise both players can be looking at very different clocks... A little while ago I stumbled across a guys site hosting some software called "Timecheat" or something which claims to exploit this issue to make it seem like you are making moves much faster than you are and give you an unfair advantage against your opponent, presumably making it appear as though your moves are coming from a slow connection. Shocking, no?
I was playing a game on www.playchess.com server at 10+5 as a guest earlier. I wouldn't normally talk about another site on here, but I thought this was funny - has anyone else ever had this happen to them, or know how it happened?
My opponent was a fairly strong opponent. Our first game, he won, and right now I cannot remember if I won the next one or not, as it is very late. But either way, I know we were on the third game...a Tromp Attack. He converted into a Stonewall pawn formation, and it was a bear trying to break through. Finally, I prepared ...f6, ...e5 and cracked one part of the wall, then ...g5 and cracked the rest of the wall. Still, he hung tough, and continued to make threats himself. He was up two pawns, but I had two bishops...and a lot of pressure. Finally, I was able to get a queen and a rook on the open g-file and pin his king to a loose rook. I took the rook, and then popped up a message -
"Your opponent has offered to take back your move"
I clicked no, but it would not go away...so I tried it again...and again...and again. Finally, the time ran out...but it did not say I won (even though I know I did). So I decided to click yes once the time ran out, just to see what would happen. It took back my move, and his move, and then asked me again. Still no win shown. So I click on it again, and the same thing happened - another pair of moves back, and again the box is up. This keeps happening. So I decide to click off the game. But it won't let me! Almost like my computer is froze. So I Ctrl+Alt+Del and get out of the program the old fashioned way. I was kind of peeved, knowing that my opponent was sore about the loss and had done something funny on purpose.
So I clicked back on the server after I logged off, and as soon as I logged on, it put me right back in the game! But the problem was, it put me back to the same spot where it took back many moves - probably at least five sets of moves, which gave my opponent some leeway to escape, or maybe at least prepare for my g-file invasion. So what did I do? I resigned the game right there on the spot, for two good reasons. #1 - I don't really want to play with a cheater who manipulates the program when he/she is not winning, and #2 - I was already peeved with the current game. I knew that I had won. I had a successful invasion, was finally up in material, with checkmate threats, only to see this "bug" that he sent to me in the game.
So my question is - has anyone else ever experienced anything like this? It maybe could even happen on this server - I don't know why it happened exactly - I thought for sure that something like that wouldn't happen on the chess server, but it shows what I know about technology! :-)