rejoining two avi files, ropey playback

[ktw]

Hi guys. Need some help with two avi files i joined together. i edited the second avi file as part of the scene was repeated from the first avi using virtual dub. The two parts joined ok and play back on pc ok. On my standalone divx player (yamada 6100) the scene jumps and cant recognise the join. If i rewind the player, the scene is blatantly there but is skipped over. Have joined avi files in past ok, but have never edited them. This is getting on my nerves. Any help appreciated. Do you think it's something to do with key frames of the movie?