If like me, you are in a poor reception area, you will sometimes have difficulty scanning for programs especially during hot weather.
I use a wireless modem/router and this is nowhere near the frequency of the tv signals, so won't cause any problem.
Make sure you have a good antenna feeding the stick, preferably a feed from your main aerial. The set top ones are not good enough, unless you are very close to transmitter..
Also make sure when you scan for new programs, you do it at the time when the channels are actually transmitting,
This is because unlike normal set top boxes, the DVB sticks don't take any notice of the actual tranmitter site, and rely soley on what it receives. Set top boxes normally read the transmitter name, location etc, and know what channels should be available, even if they are not transmitting at the time..
Hope this helps.