With the owners' permission, I tried two other random WPA APs to no avail -- no handshakes captured. I manually disconnect and reconnect the clients, as well as successfully deauth them, but nothing; I don't capture any handshakes. Tried both BT4 and BT5 again. As before, when the same APs are set to WEP, I can aireplay and capture IVs just fine.
I read somewhere on the forums that this may have something to do with the modulation and that they should be set to the same, but the command "iwconfig wlan0 modu 11g" is apparently not supported by the RTL8187 chipset, nor any other change in modulation.
I have also tried changing my MAC to a client MAC and disabling that client, but that has no effect; not that it should, since the APs are not set to filter by MAC.