Hi Alok,
I'm not sure if this is the same problem, but we ran in to an issue where a student bridged their wireless interface with another interface (not sure why) and it was triggering spanguard on the AP port. The AP would disconnect, the laptop would associate with the next closest AP and the same thing would happen. It took us a while to track down the laptop and even longer to figure out why it was causing it.
Good luck,
-Rich P.