HEAP ZONE ERROR SOLVED!
I had the same problem and it drove me yompy.
I finally figured it out.
The heap zone is the hard drive and the "not enough room" is really refering to "not enough contiguous space".
I optimized my volume on the drive and it took me from MB of Contiguous Free Space (though there were 500 GB of it total) up to GBs of Contiguous Free Space.
I now no longer receive the same warning, ever.