Printing ps files w/ 8.2

I've just switched to cups as print server. It's very nice except for one strange thing. There are some ps files that won't print! I send them to the printer, they're in the queue and the seem to be printed - they just never actually come out as paper. I can't see any real difference between the ones that will and the ones that won't - they both look OK with gs. I can't see any trace of them; no entry in any log. If I convert the nonprinting files with ps2pdf or ps2ps they print fine too. What is the best idea? Any way to see what's actually going on? Or is it better to ps2ps all ps files - and if so, how to do that with cups ??