Connecting to wireless network when more than one is available

I am unable to connect to my wireless network whenever
there is another wireless network operating in the same
area. I can connect when there isn't one operating nearby,
and am knocked off my own wireless connection whenever
another wireless network is turned on. XP recognises that
there is more than one network available but is unable to
reconnect to mine. I have to unplug my wireless adapter,
and then reconnect it, to get back on my own network. I am
using XP to configure my wireless network, WEP 64 bit
encryption, etc.

Thanks in advance for any advice