a couple-a things
When your link drops does it try to connect to another nearby access point? Depending on where you live you may have neighbors with the same setup (apartment complexes are a killer). If this is the case your NIC may be trying to connect to other routers (i.e. if you move about, etc.) Be sure that you are using different settings than the default. True, each wireless access point is different, but there should be a "prefered access point" setting somewhere in the configuration. Find out what your routers mac address is and input it into this "prefered...so on and so on".
you can also try to change your wireless channel. Typically everyone uses either 6 or 11. Try one or the other and see if it helps.
Additionally, after it drops try to consol into it (type 192.168.x.x or whatever your routers address is) and check the status of the device. If it looks like it's still connected, try renewing the DHCP. This should initiate a new connection.
Let me know if this helps. If not, I probably got a few other things you could try.