I did notice one thing when watching replay though. From my PC, it looked like this: in lap 32, when I came out of the first corner, the lag started and all other cars disappeared. Right after the first split, I got disconnected. But when watching replay downloaded from the OLFSL site, I was not in lag after that first corner. So the data from my pc was successfully recieved by the server, but the server did not send out the data. Maybe there was something wrong with the connection of the server (line full) and server could not send out data to all the drivers.
I don't think it was the ISP fault, because two of pool 1 drivers have the same ISP as me, and they were not disconnected.
I'm also using fraps and it works fine. Make sure you put half-size video option and not too many fps. Also when recording set LFS replay speed to 0.5 or 0.25.