Without delving into the internals of HTSP streaming (because I can't!), is VLC on the same box as the tvheadend software? As XBMC? Are the network connections equivalent? CPU/GPU, RAM utilisation, etc.? What sort of channel is it - SD, HD? - does it need hardware acceleration, is that switched on in VLC? What about mplayer or some other client application?
It's a process of elimination... I can certainly stream to VLC (checks... yes, works find for an HD signal over 802.11n here), so it's not a clear fault with the code.
What version of tvh are you using, by the way? That URL looks like the old format, so I wonder if that's related...
