Media Center Extender (Vista + XBOX 360) intolerably slow

I've had ZERO success in playing MCE content - ie live TV,
recorded TV etc on the XBOX 360. The menus are intolerably slow, taking 5-30s to
respond. Eventually when streaming starts I get a couple of seconds
then streaming stops.

I have Windows Vista Ultimate x64 (SP1 RC)

If I try the performance test tool I get an error:

Unable to Measure Network Performance

A connection to the Windows Media Center Extender cannot be
established. Please make sure that the Extender device is properly
connected and that the start screen is visible.

This occurs with firewall and av all stopped. I (no longer -- thanks
to dynamic disks!) have OneCare installed, and the Xbox most
definately can connect to the PC as it manages to bring up initial
windows albeit with slow response.

Host machine is dual core (Pentium D 820) with 3Ghz ram running Vista
Ultimate x64. TV progs are on striped disk (2 devices). As before
network throughput is in the 16-20 Mbps range over 802.11g

Wireless power saving is off, and ping time is ~1ms.

Both devices are on same subnet with no additional firewall rules etc
set on router.

Finally Video streaming (mpeg4) and music streaming (mp3) from a PC ie to
Media Player using the xbox 360 dashboard works *very smoothly* meaning there is something wrong on the media center/xbox side.

Anyone have any ideas? Other than this the xbox is very nice, but this is frustrating!

Wharfdale DVDRHD400F dvd recorder

Today I decided to pickup a "cheap" dvd recorder to offload some stuff from sky onto DVD.

I reserved this:
533/5811 Acoustic Solutions DVD80RW300 DVD Recorder with 80GB HDD

When the item came out it had this code, but was actually a Wharfdale dvdr400f. Still an 80Gb drive, but with Freeview. This is *not* what was clearly advertized in the spec, but looks a great deal to me... in retrospect the item listing does mention info about freeview under Additional Information, I'd just figured that was generic... NONE of the other half price recorders appear to mention freeview....

Thoughts so far:
* Surprised to get freeview!
* RGB-in is supported on SCART #2 so recordings from sky are crystal clear (despite this being referred to as rgb out in the manual... rgb out is fine too in any case) - note many recorders don't have rgb in!
* box is fast and menus are very clear
* remote is the usual cheap type - too many small buttons IMO (something sky have just right for sky+)
* DVD erasing/writing is quick
* Programs can be split on HDD
* Recordings can be made direct to DVD or to HDD (and later copied)
* Freeview works well
* But the freeview tuner is clearly internally connected by composite not RGB so dot crawl can be evident (this really surprised me, seems like a silly oversight!)
* No firewire (which I knew)
* Recording length is HQ/SP/EP/LP/SLP
* RGB passthrough (in via SCART 2 and out of SCART 1) in standby works as long as unit isn't in power save mode

Still pretty good for 59.99.