there are some reasons of 100Mbps NIC connection (especially on HP DL380 G5) on Vmware ESX/ESXi v4 and v5

1. HP DL380 G5 have ILO NIC on the first NIC so when it's in shared mode it's act as a 100Mbps or eventually 10Mbps NIC

2. ALWAYS check the cable, its really often happen that the cable is a real problem, of course patch panell too

3. server/NIC firmware problem, it's happens but not so often

4. broken NIC, it's hapen rather rare

5. bad negociation on switches and NIC... it's happens sometimes

regards

NTShad0w