I just upgraded from BM 3.7 to 3.8 and from NW 6 to NW 6.5 sp1
After a fresh start, everything seems to work fine. After 2 or 3 days
everything starts to slow down. The mail server logs start getting
more and more "connected to x.x.x.x but connection died, connection
defered" messages, web browsing slows, outside access to our web
servers and remote access PC's practically halts, FTP transfers start
to stall and using the GW client over the internet takes 10-15 minutes
to login. It keeps getting worse and worse until I unload and reload
filtsrv and ipflt modules. Then everything returns to full speed again
for another few days until the problems slowly return.

Could you suggest some things to look at before I open a support