I had ball ache with my sigma 1600 DTS too. Everything here in my area of Germany seems to interfere with the wireless transmission, so consequently it only worked some of the time. I got really annoyed at having shelled out so much for the thing though, and wrote an angry email to Sigma to cry about it. They responded saying they knew that the streetlights were at fault, but they would replace my computer with an updated version for free. Well done for trying to rectify the situation, Sigma! They also admit however, that it won't work around the 65xxx Postfach area in any case (where the streetlight mothership is, or something).

Despite Sigma being nice and trying to fix everything, I'm definitely a bit sceptic about buying anything more from them.