NAV 2009 causes network slowdown

I tried support live chat twice, but got disconnected after 5 and 30 minutes and put back into the queue, so hoping to find some results here.

 

With NAV 2009 active, shared folders over gigabit LAN cap at about 15MB/s.  Disabled, copies go to 75MB/s.

 

Windows Vista Ultimate 64 bit SP1 with latest updates

NAV 2009 with latest liveupdates 16.2.0.7

A few other productivity apps (Office, Photoshop, etc.) but nothing LAN or firewall or AV related

Windows firewall enabled

Windows Defender installed but was disabled as part of NAV installation

Clean install on a formatted drive yesterday

Marvell ethernet controller

Intel i7 920 CPU, 12GB RAM, Intel 80GB SDD x 2 RAID 0, Asus P6T Deluxe with latest BIOS 1102

 

Connecting to a shared folder on a Windows Home Server.

Vista reports copy of various files from WHS to desktop of only 12-16MB/s.

Updated Marvell driver with one from Marvell.com instead of the one from Windows LiveUpdate - no change

Disabled Windows firewall - no change

Switched to 2nd LAN port (same chip, same two drivers, different port) - no change

Tried same share from another PC on same router, got about 60MB/s

Verified in Windows network center that connection is 1gbit

Verified local file copies are normal speed (>100MB/s)

Disable and enable the Symantec Intermediate LAN driver - no change

Disable and enable Intrusion prevention on NAV - no change

Change server under Home Network to Server PC - no change

Internet downloads seem to match expected values - speedtest.net shows 25mbps

Disable NAV Auto Protect using system tray icon right click menu - copy speeds improve to 70-80MB/s.

Reenable and speeds drop instantly.

Rebooted PC, Router, and Server - no change

 

Any suggestions?

 

Thanks