Connectivity issues

I'm looking for direction to locate the source of connectivity problems
we're having with DB2 run off of an IBM I-Series (AS400) running OS400.
The symptoms are very sporadic and they don't always happen together but
they happen every day or two.  Also, I'll provide my observations but if
other information is needed, ask and I'll get the appropriate
information.

We are in an Windows XP desktop enviroment using IBM's ODBC drivers to
connect to the AS400.

1.)  ODBC receives repeated 'Connection login timeout' errors from the
I-Series ODBC driver while the server is accessible from the Navigator
and all mapped drives are accessible (I run trace routes _everytime_ the
connection goes down.. sometimes the trace routes go through fine while
I can't connect and sometimes they can't get through indicating that
it's isolated from the network).
2.)  At times (like today), I can get to the I-Series through the
Navigator/Mapped drives, but not through ODBC with the timeout error and
a co-worker has a different set of symptoms... she can get to it through
the navigator, but cannot map a drive.
3.)  The server is up, but loses all connectivity to the network for 6
minute spans (sounds like it's losing connection and not trying to
connect again for 6 minutes)... at this time other servers on the
network are all accessible (other servers being Windows based). 

 
Thanks in advance
 
Victor Mallory
Senior Systems Administrator
Indiana University Foundation
Showalter House
1500 St. Rd. 45/46 Bypass
P. O. Box 500
Bloomington IN 47402
voice: 812-855-3120