>I believe it's a system problem, not the HDF library.  I'm just looking
>for a manual flush that would alleviate my problem.  I appreciate the
>help, and If you all do find a way to manually flush the buffers, let me
>know.

"Flushing" data means an application is very paranoid of the data 
integrity and is willing to initiate a real disk write and WAIT until it 
is finished.  It is a requirement of data integrity at the cost of
response speed.  You can keep telling the system to flush the
data out but the data can only move at the limit of the I/O channel.
If you want your memory to be freed up sooner, you would have to employ
one or more of the following:

1. faster disks and faster I/O channel;
2. more memory;
3. more disks and use stripping;