This may sound stupid, but check which side of the TiBook faces towards the base station!
If I go to the garden and I place my TiBook so that it faces with either the back or the front towards the base station, I have nearly no or completely no reception. But when I turn it so that the two plastic "windows" on the side of the TiBook, in which the antenna are, face towards the station, I get between two and three bars of reception....compared to no reception that's quite interesting I think....
btw: I know it sounds crazy, and if somebody else would tell me this, I'd say he does something wrong, but it's really true...