GW 8.0.2HP2 running on Windows 2008 R2 64bit

We have One PO that occasionally without a pattern gets Really slow., All users complain of being Locked up or almost locked up.
The CPU Spikes at 100% for about 10 Min with the gwpoa.exe *32 Service being 96% of the load.
During this slow period If I compare with a time when it is OK, the only difference on the Status screen is the
C/S Handler Threads shows 28 Total 28 Busy
Message Worker Threads 6 Total 4 Busy
IMAP Threads 8 Total 5 Busy
After the threads clear (Usually about 10 min) everything is great for 1 or 2 hours.
Any suggestions of what to look at?
Thank You in Advance !