I hate to confirm it for you... But Server 2008 isn't supported on ESX 2.5.x.
Additionally, the VIC 2.x, will only connect to an ESX 2.5.x box using VirtualCenter 2.5.
Can I ask why you haven't upgraded to ESX 3.0 or 3.5?
Jase McCarty
http://www.jasemccarty.com
Co-Author of VMware ESX Essentials in the Virtual Data Center
(ISBN:1420070274) from Auerbach
Jase McCarty - @jasemccarty