Why doesn’t Windows 2003 R2 Standard Edition like Vista?

We had a Blade Server installed with Windows 2003 Server R2 SP2 Standard Edition. We were told that Vista is not compatible with this server. I haven’t gotten an answer to why, especially since we’ll have the server for a few years and XP is being fazed out in a few months. I hooked a Vista machine up on the network and it was unusable with the server. Folders on the server took several mintues to open on the Vista machine and server applications would not run at all.