You can use a SNMP manager to monitor the memory utilization. I am not a SNMP expert; so that I cannot provide the exact MIB for this.
Alternatively, you can telnet to the AP and do the
show memory.
There is an internal known bug open for this problem:CSCeg14657. As the bug is found internally, you cannot see the bug details of the bug.
The bug is in a severity of 3. I suggest you to open a TAC service request.