Right, recently my Desire has developed an annoying glitch...
If I leave 3d or WiFi on and the phone in idle it will turn off the WiFi or 3g if nothing happens, ie an email or tweet received.
The icon in the display will be gone, and internet does not work. But the widget I have on my homescreen will show as on. Sometimes If I start using the net it will refire but mostly it won't and I have to cycle it off then on again.

Anyone else struck this? It's an unbranded Desire from Clove running stock unrooted 2.29