Ok, thank-you very much for the replies, I guess I better tell the whole story, I was trying to avoid for the sake of brevity...
1. Original issue was quickly flashing anti-theft light (no-start). I tried to fix it myself (using the "everything you needed to know about PATS" thread), but couldn't, so I had it towed to my trusted service station mechanic, who couldn't figure it out, then had it towed to the dealer. It started right up for the dealer (although was now running very rough), so I came back and drove it home. Next day tried to start it from home, same problem (blinking anti-theft, no start). So had it towed to the closest (different) dealer (this was a mistake I can see now), who "fixed" it by replacing the anti-theft module.
2. I then went back to the original dealer to fix the running rough problem. They said a broken heater control valve was dripping water on the number 2 cylinder plug causing misfires, and the EGR valve was unplugged. So they fixed this (charging me 2hrs plus parts) and told me to come pick it up.
3. When I came to pick it up, it wouldn't start, rapidly blinking anti-theft. That is where my story starts above (them telling me their diagnostic says replace the PATS module, but the advisor saying that couldn't possibly be it as PATS modules don't go bad that fast (<100mi)).
The car is only worth about $2000 now, but I really like it, I enjoy working on it, participating in this forum, and it still is in really good shape. Has (until now at least) been by far the most inexpensive vehicle I've ever owned...