HELP: Strange memory/NIC problem

How can a network adapter(NIC) affect or be affected by the amount of
memory recognized by Windows? I have 1GB of memory consisting of a matched
set of Kingston KHX3500 512MB DRAM's. The m/b is a MSI 865PE Neo2
FIS2R(MS-6728). The NIC is built-in and uses the Intel 82547EI chip. Vcache
is limited in System.ini to 512MB.
If I disable the NIC in BIOS I can boot with no memory limit set. With
the NIC enabled in BIOS and installed for use in Windows the boot hangs at
"Starting Windows 98". If I limit the memory to 768MB through Msconfig I can
boot fine with the NIC ready to use. I've had the memory up to 819MB before
hanging repeatedly. With the NIC enabled in BIOS but NOT installed in
Windows I have no problem.
Other than memory, what could cause this? I don't have another GB of
memory sitting around to be able to swap. I did switch them around, but it
made no difference. I've Googled the 'net and newsgroups and found nothing
to help with this strange problem. I e-mailed MSI a month or so ago and they
were no help(they did answer.) Different drivers don't matter either. I
would really appreciate any ideas.

Thanking all in advance,
Wayne R.