If you are using cogswap from the memory card the TOC from the ps1 trigger disc has to be bigger than the backup ps2cd you are playing (obviously this doesn't apply to dvd's as the TOC is refreshed anyway)... i found this out this weekend after some experimentation .... driver and ff7 disc1 i found from my ps1 collection have 620mb tocs which is fine for lego starwars at 607mb