Vista - Xbox360 Extender Library Slowness

Issue:
From my Xbox360, whenever I go into my library on my Vista Media Center it takes 30-60 seconds to pull up anything. Even when I go to play anything it takes the same 30-60 seconds. (This only occurs when access content from the extender.)

Everything works fine when accessing it from the computer.

So I think I isolated it to my home network. I ran a sniffer (Wireshark) on my network (everything is wired) and it shows a ton or lost packets and re-transmits whenever I do the above (and only when) due to Checksum errors.

I have replaced all cables, replaced the switch between the two (flat network), Updated All drivers on the MC and fully updated the Xbox360. Even adjusted the Broadcom NIC settings for Offload Checksum, Rx\Tx Pause settings, etc. All with no luck.

I am beginning to suspect the Xbox360 NIC, but am curious if maybe you have seen this issue before?

Any thoughts?

Here is my setup:
Vista Ultimate, 3GHz CPU , 2.5 GB RAM, ATI 8300 Videocard, 1.5TBHDs, (2) ATI HD-650 Tuners
Linksys wrt54gL router
Xbox360

Are you running the windows firewall? do you have a 3rd party software firewall on your machine? Might try disabling it. I figure you've probably already done it, but sometimes its the simplest things that people overlook. That extender services uses a crapton of tcp/udp ports.

I seem to actually be experiencing the same type of problem but only with Vista 64bit. Selecting anything (scrolling through recorded episodes etc.) usually takes 60 seconds plus for it to switch. Streaming also skips etc. I did a clean install of Vista Ultimate 64 and I experienced the same issues. Then I installed the 32bit version and everything is working just fine. This was pre-SP1 so I haven't attempting to try again.

E6600 @ 3.0Ghz (Yes I have tried stock speeds, no help)
8800GT
4GB RAM
Gigabyte 965P-DS3
Hauppauge PVR-500MCE

Buffalo WHR-HP-54G (Running Tomato) <--- connected to PC
bridged to...
Linksys WRT54GL (also running Tomato)<--- connected to Xbox 360