Thanks for the responses guys, good to know it's not just me! As I said I don't use melamine very often, but I don't remember this happening on the last job about 2 years ago. However that particular batch was a non-stock woodgrain that came directly from Canada, so maybe a better grade? I have no idea what brand this was, I didn't specify when ordering as I didn't think it was necessary. I will bring it up with the rep when he comes by next time though.
Jonathan, what else can I blame if not the melamine....it's moving! I thought the stuff was more stable than this but I guess that's my own ignorance. These are all tall Euro wardrobe cabinets at roughly 87" tall so as bad as it gets I suppose. I couldn't feed any slower, as it was I had to back the sheet out of the saw after cutting about 10" or so and start over as it just wouldn't feed. After the initial rips I replaced the blade with a freshly sharpened blade, (all fairly expensive double sided melamine blades fwiw), and still had problems even on the short crosscuts!
Anyway I used the track saw to straighten the initial edges and then re-ripped on the table saw to get a clean front edge. Ended up spending a good half a day just to get the parts cut for 6 tall wardrobe cabinets.....but I did get them cut!
thanks again,
JeffD