What is a Unrecoverable Error 668 - Eval Stack Fault?
 A locked VM segment has stopped the Eval stack from growing
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 This would normally occur in a real mode program under a very tight memory
 situation, where the Virtual memory system has allocated and locked an area
 of memory, from the DS available memory, for use as clipper free pool
 memory.

 The Eval stack cannot grow into the DS available because of the locked
 segment and hence this error message.