I'm guessing that some of the .AVI files are using the MJPEG codec. If so, Windows Media Player has a built-in MJPEG codec, Vegas does not. You need to purchase a VFW-compatible MJPEG codec. There are several;
Or it might be a DivX or Xvid video. They just don't import to Vegas 7 regardless what codecs are on your system. Only the audio comes in. Sony really need to fix that.
OK, thanks for the checking program Gspot. I used it on the file made by my Samsung Digimax I6. It appears they are Xvid MPEG4 files. So what is the recommended codec for these? Thanks