I have nw5.1 sp6 and BM 3.7 sp3 with last patches..installed with C.
Johnson's BM Book.

used services/proxies HTTP, FTP ,Generic TCP and Socks
Only one acces rule with indexed logging for denyed URL-s..

all works well except socks gateway sometimes. Sometimes, sometimes with no
reason, if you look real time activity of IP Gateway
(Nwadmin-tools-Bordermanager-IP Gateway) workstation hangs and server CPU
utilization rise to 100%. and only way reboot workstation and reload
proxy.nlm on server..
By the way the same is for Proxy cache monitor...

is any ideas ?