There are several things that could/will help you. I had a similar problem and did all of the following, and now I never have a problem.
1) Change your wireless network to a different channel. I.e. get off the factory default channel. For D-Link equipment this is channel 6, I'm now on channel 4.
2) Name your wireless network something besides the default name. I.e. call you network something like your last name, dogs name, etc. For D-Link equipment the factory name is 'default', now I'm on a network named after my last name.
3) Setup encryption on your network. A simple way to do this is to use 64-bit hex encryption which requires 10 alpha-numeric characters 0-9 or a-f. I would recommend your phone number with area code (10 digits). Unless you need more protection than that.
Basically, after doing the following and connecting to that network, I always connect to that network, without problems. I think it has to do with the encryption key. Since I had to enter it into windows, it remembers that as the most prefered network.