MCE over Apple Airport Extreme/Express combo

[Shan]

Apologies for the repeat post (I stuck this on the end of an old but related thread yesterday) but this is driving me nuts!!!

'The Enemy' has finally had enough of blue cables down the halls so here's what I'm trying to do:

I'm a bit of a Mac-o-phile on the quiet (comes from running Windows networks for a living) so I have a Gig Airport Extreme wired to the Vista MCE box, XBOX360 hanging off a brand new Airport Express, all set to 5Ghz 'n' but have a funny problem.

Xbox streams fine direct from my Windows Home Server through the Media screen on dashboard (even Hi Def files), Media Centre extender mode works fine for stuff I've downloaded and play back via Transcode360, but playing back anything from recorded TV just gives me a black screen. The progress bar is going across as if the file is playing but no pic or sound.

I don't see why DVR-MS should be blocked specifically - anyone have any idea's?

P.S. Network test from the 360 shows 1 bar into the HD range pretty solid.