Since a repeater uses the same SSID, you can't really control this easily. If your client has a setting controlling roaming, you can try changing it.
Your post made me realize the difference between a WDS repeater and an AP. My current setup is a WDS repeater. I will set up an AP when I can, but right now that's not possible.
The IP method didn't work, but so far the BSSID method is working. That seems to have fixed the network dropping issues as well.
Using inSSIDer on the laptop which was having the dropping issues, the following image http://img213.imageshack.us/img213/9701/screenshotinssider1.png shows the signal strength of the router (blue line) which in the basement and the repeater (light orange line) which is on the first floor. The laptop is on the second floor. All three devices are nearly on top of each other. The repeater's signal has fluctuations of 10-20 dB or more. Maybe this could explain why the laptop kept switching which device it connected to. The more important question is, is it normal for the repeater's signal to vary so much?
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