Choppy video since upgrading to Vista on the server & new hardware

[Destro]

I have been running XP Pro on a Pentium 4 as my server for quite a while with no issues. I've used all types of clients, SageTV Client, Placeshifter, HD100, MVP.

I recently upgraded the server to an Intel 2.5Ghz Dual Core (Wolfdale core, latest stepping), 4 GB RAM, WD Black edition SATA drives with 32 GB cache... plus Vista 32 bit Ultimate as the OS. Everything is on Gigabit all the way through. Now my performance is 10x worse than with a 5 year old PC. From the client, menus are sluggish, videos are choppy, and when watching the network traffic on Task Manager with a video playing on the client (both from the server side and client), it only registers as .5% network utilization. Server CPU stays around 1-2%. I am only doing SD video, no HD.

Running a LAN speed test to the server shows I can write to the server at 468 Mbps and read at 107 Mbps, tested with 100 MB chunks, so Windows-to-Windows network speed is not a problem.

Any suggestions? I've read many other forum posts about choppy video and Vista issues and none seem to fit my problem.

Also, when I enabled file sharing on the server (to run the benchmark), my SageTV clients could no longer detect the server. Any idea why? I had to do a System Restore to get Sage working again.