Internet Connection Sharing Problems

I am running Windows 98 SE on my PC as a
server for Internet Connection Sharing. I
have a dial up account that I am sharing on a
home network with 2 other client PC's. I have
set it up with manual IP adresses on the
server and client machines. I can use the
internet on the client machines ok (for a
time). My computer is normally very stable
and I have a good internet connection which
causes me no problems. When I use a client PC
for using the internet (over the LAN) It will
sometimesafter maybe 20 mins. stop accessing
the internet even though the server is still
dialed up. When I check the server PC I find
it has come to a hault and is not responding
or responding very very slowly (like take
60sec to open a window up). If I try using
the Internet on the server PC (the one that
is directly connected to the modem) or
running games over the internet there is no
problem. If I try running an game over the
internet on the client PC (over the LAN) It
will start workingthen withing about 1-3
mins slow right down and stop and my server
PC (running the internet connection sharing)
will stop respoding.

I have checked the support knowledge base on
the Microsoft website and have found nothing
helpfull. I am positive I have set up the ICS
according to the Microsoft Webpage
information. I have tried uninstalling ICS
and reloading it... nothing different
happens. I have also loaded the latest
Anti-Virus update for my virus scanner.

How do I get Microsoft's Internet Connection
Sharing to work reliably? or is that out of
the question?