http://www.sysinternals.com.

Get the (freshly updated) tools to view handles, and see if there is a handle leak. Also "process explorer" will give more details than just looking at the totals in Task Manager.

Reduce the available memory and run again. Does the problem spot pull back as well? Is it the same spot on Unix as well? If always the same spot, it sounds like something in the logic itself, not memory.

—John