We've just installed a UC560 for a client and we're experiencing the same problems as described in this thread (conversation stops in one direction for 5-10 seconds at a time).
There are 4 x AP521's and 15 x 7925G's. The 7925G we tested from was stationary, so it isn't a case of the phone moving from one AP to the next.
Was this ever resolved? I couldn't find a solution on the net and I can't really open a TAC at this time as the WAN link hasn't been setup
Thanks in advance.