Vpn disconnects

Hello,
our config:
hardware firewall -> isa -> server (win2003server with ias)

We connect with a vpn tool to our hardware firewall. Next we open a
(windows) vpn connection to our isa - server and login our domain. Everything
works fine
but after approx 10-11 minutes the windows vpn connection is dropped.
I couldn't find any solutions to our problem. But this weekend i ran into
this kb.
http://support.microsoft.com/kb/875501/

Does this solution apply to our config or not ?
Maybe you have some other suggestions concerning our config or problem!

Thx.