We seem to be having a very similar issue! MSM 760 with approx 70 APs (MSM422/MSM460).
See the following for some of the testing that we have done:
http://h30499.www3.hp.com/t5/MSM-Series/MSM760-Clients-loosing-network-connectivity-ping-times-5-10-full/td-p/6716088#.VPe2dmB0270
We also tried changing all of our APs to Static addresses, but this didn't seem to make any difference, except it added some more errors in our logs (see bottom two):
Mar 5 02:41:21 warning eventmgr EVENT[26814] AP (name='I01') is silent. It may still be providing services but is unmanaged. Reason: (value='Secure connection to AP went down')
Mar 5 02:36:20 warning eventmgr ALARM[4] <- EVENT[25263] Raised. AP (name='00:24:A8:86:3F:7E') is silent, it may still be providing services but is unmanaged. Reason: (value='Secure connection to AP went down').
Mar 5 02:36:20 warning eventmgr EVENT[25263] AP (name='00:24:A8:86:3F:7E') is silent. It may still be providing services but is unmanaged. Reason: (value='Secure connection to AP went down')
Mar 5 02:09:40 warning eventmgr ALARM[3] <- EVENT[21171] Raised. AP (name='00:24:A8:87:E0:5C') is silent, it may still be providing services but is unmanaged. Reason: (value='Secure connection to AP went down').
Mar 5 02:09:40 warning eventmgr EVENT[21171] AP (name='00:24:A8:87:E0:5C') is silent. It may still be providing services but is unmanaged. Reason: (value='Secure connection to AP went down')
Mar 5 00:32:33 err rccd pb_client: not connected to '169.254.0.52'.
Mar 5 00:32:33 err rccd pb_client: cannot connect to 169.254.0.52: Connection timed out (110)