Load Balancer & Unable to write data to the transport connection

[DT]

We have service oriented architecture
that comprises of a number of Win2k/IIS boxes.
Some of these web service applications access an AS400
system for data acess (We are using HitSoftware's Ritmo .net
native driver). For fail over we route these requests
through a hardware based load balancer (BigIP).

The BigIP allows us to fail over to a secondary AS400 system
in case the primary one fails.

On occasion we get the following message under high load
"Unable to write data to the transport connection". Under
a constant barrage of requests, the webservice eventually
fails and does not recover, requiring us to perform an iisreset.

We decided to bypass the BigIP and go directly against the AS400
itself. The errors went away. Has anyone experienced
such a problem and figured a way to configure their load balancer
to get this to work correctly?

My next question is whether anyone knows in particular how socket
connections are pooled with the low level .Net architecture, especially
when a hardware based load balancer decides to fail over to another box.
How long do such connections live?

Any tips would be appreciated.

Thanks,