Usually, if you are using a debug build, you'll get a complete stack trace with line numbers. I find those very helpful.
Flex SDK Developer
Adobe Systems Inc.
Hmm.. I do get a stack trace... but nothing useful that I could find. I'll run it again in a bit and post the stack trace here.
Scratch that. You are right of course. I swear that I combed though that before and couldn't find anything useful. Looking at it again, it doesn't tell me the problem class, but I do get the line # for the readObject() that it's failing on. It's reading a collection of mixed types so I still don't know which one is the problem. But at least it's WAY narrowed down now.