The Application Heap Zone is bad

[lynch@aristotle.ils.nwu.edu (Richard Lynch)]

Using MacsBug and an inordinate amount of crashes and some wild guesses, I
have managed to elicit a message from MacsBug that the application heap is
bad.
Unfortunately, this doesn't tell me a whole lot.
We are using a lot of icons, picts, and even some self-defined "region"
resources and trap calls such as _LoadResource and so on.  I believe I am
calling these trap calls correctly, and they seem to work fine, but...
Sometimes on creation of a window with a background pict and some
dialog-items that draw up to four icons per dialog-item, I get a nice
crash.
MacsBug stack-crawls mention a lot of unintelligible numbers and something
like N._XNnn as a procedure name.  (What the heck is that?)
I tried cutting out the most recent additions (three screen-sized PICTS
created with Ultra-Paint) to our resource file, but that didn't seem to
help.
SO, any guesses as to the most likely corrupter of the Application Heap?
Any suggestions on how to figure out what's going on?

"TANSTAAFL" Rich lynch@aristotle.ils.nwu.edu