[fpc-pascal] mysterious crashing, maybe related to setlength

[David Emerson]

My program is crashing, and I just can't figure out why. Heaptrc has 
given me this rather cryptic info:

Marked memory at $B79BA208 invalid
Wrong signature $000020D8 instead of 8E1C71B6

Using lazurus's step-into functionality, I've it down to the line where 
it's crashing -- seems to be crashing upon completion of a function. 
Alternately, I can get it to make a similar crash on setlength of a 
dynamic array to length 0. (The array has refcount 1.)

I haven't been able to reduce my code to anything reasonable; whenever I 
cut out seemingly irrelevant/unrelated sections, the crashing stops.

Thanks for any advice!
~David.