What kind of router? Any error messages or log files?
I have seen some strange spanning-tree issues where two or more APs bridged on the same RF channel with the same SSID and credentials managed to link up over-the-air and cause a bridging loop. Fun to track down as they were some distance apart and the RF propagation had to be just right. Not Adtran gear.
What software versions are you running on your AP's and vWLAN?