Nothing is forced on the switched we had tried. 2 switches were gigabit, while 2 others were 100. On each switch, the nics auto-negotiated to either gigabit full, or 100 full.

The net admins couldn't find anything odd on the switches error wise either.

Really puzzling problem so far. At first we had just figured it was a tg3 issue, but once the Intel nic was thrown in, it really confused us.