Need help with wireless network

I have a Linksys wireless network system (g system) at my office and my house that I use for Internet access for my laptop. Recently, the office below me and my neighbor have also installed a linksys wireless system. As a result, I get a message on my laptop that more than one signal is available and I then lose my connection to my network. I must then manual connect to the system again until I lose connection once again. How do I setup the network system so that I keep a constant signal and do not get cut off?

I had a computer guy (technical term) change the settings to my office Linksys router were my router was renamed "linksys0". He also enabled the WEP security feature since other people with wireless cards could use my Internet connection. I can now see the two separate signals (linksys and linksys0), but I still get cut off from the signal. The unit at my house still shows just one unit ("linksys") since the router has not been renamed.

Any suggestions would be appreciated in preventing my signal from getting cut off. Prior to the installation of the other units I never lost a signal to the router and did not experience any problems.

Thanks.
Ken