Recently, we encountered issues with Virtual Server 2005 on the new Dell 1950 servers. Everytime, a virtual server is switched on, the host network doesn't seems to respond.
After much investigation, it seems that the problem was caused by the specific Broadcom network card.
Solution: Install the MS Win 2003 Scalable Network Pack Release:
Base KB http://support.microsoft.com/?kbid=912222
SNP home http://www.microsoft.com/technet/itsolutions/network/snp/default.mspx
SNP FAQ http://www.microsoft.com/technet/itsolutions/network/snp/faq.mspx
Whitepaper http://www.microsoft.com/downloads/details.aspx?FamilyID=6aee2e62-b708-44c1-babe-fc0e7b0f02bd&DisplayLang=en
Thanks to Baillard and Tom Che (MSFT) for the speedy fix.