Lisp heap vs. Mac heap

[paul@informatics.WUstl.EDU (Terrance Paul McCartney)]

I am having what appears to be a problem with memory allocation.  My program
uses several GWorld offscreen bitmaps (700 x 500 pixels, 1 bit depth).
Most of the time when the program tries to allocate these bitmaps (BTW, using 
"oodles of utils" to do the allocation), everything works fine.  Sometimes,
for no reason, I get a mysterious "Error -108" which I cannot find in any 
of the manuals.

Memory is not a problem.  I am running MCL with a 19 Meg memory partition
(of which, my program actually uses about 5 megs).  However, it seems as 
though MCL has a problem transferring free memory from the Lisp heap to
the Mac heap when I attempt to allocate the bitmaps.  Is there any way to
control the sizes of the Lisp/Mac heaps so that this problem does not occur?

Thanks in advance,

- Paul  (paul@informatics.wustl.edu)