Depending on the brand of WIFI Router and the protocol (802.11b/g/n) that you are using, it is very possible to end up with 'dark spots'. Adjusting the antenna position will usually cure the problem if it is a simple signal problem (vertical / horizontal positions). Also if you want to dump out some extra bucks, you could also change the antenna on the router for a high gain antenna. D-Link makes one for about $35.00. PS... although I have seen some WAP conflicts when channel is on auto scan, this is usually pretty rare: In general it's a first to the post for channel selection, and if the second place finisher tries to use the channel allocated to the first place finisher, it should detect the other WIFI device's info and choose another channel. Also on conflict the WIFI access point should re-scan for an available channel. If both WIFI networks have the same SSID, that might cause a seriously weird result!

Is your router's wireless protocol 802.11b or g. I sincerely hope it's not an 'n' class wifi device as I don't believe the Pronto TSU's support 'n'. If it is a 'b' class wifi device it will be running rather slowly as 802.11b has a tiny transfer rate. 802.11g rips along at 54mbps (although that's its 'rated' speed).