Chris sent me this question:

I have a load balancing team configured with 2 intel mt 1000 gigabit cards.
My guest operating system looses network connectivity If I leave it idle for say 10 minutes or if I close out and come back in after a while.

The information you need is here, basically you should try removing the team first and see if this resolves the issue, before contacting your hardware manufacturer.
http://support.microsoft.com/kb/888747/en-us

Someone may have other suggestions, which they can comment on here.