About six months ago, we bought a D-Link DNS-320 ShareCentre, installed two 1TB Seagate HDs, and began using it for our fileshare. Access and speed was OK, but not great.
Since about two weeks ago, our access to the fileshare has been intermittently very slow. Files (any size, 1 KB up to megabytes) load after a long hang-time, or don't load at all. The delay is far, far beyond the difference between 10/100/1000 bps connections. Navigating between folders, saving, moving, copying, and deleting files also have this intermittent hanging.
 TP-Link TL-WR841N, operating LAN only
 D-Link DNS-320, firmware v 2.03
 computer running Windows 7 Professional 64bit, on-board Ethernet connected to router
 computer running Windows XP
Trials with network configurations:
A)  connecting , , and : both  and  experience problems connecting to 
B)  connecting  and  only ( disconnected):  still experiences problems
C)  connecting  and  only ( disconnected): no problems
D)  directly connected to  via Ethernet:  still experiences problems
E)  directly connected to  via Ethernet: no problems
Further trials with configuration (A):
i) Configuration (A) above, booting  in Windows XP (from separate HD): no problems
ii) Configuration (A), booting  in Windows 7 Safe Mode with Networking: no problems
- I'm running Comodo Firewall on . The problem persists when I disable it.
- Both  and  were on old (2010) firmware, and are now running on up-to-date firmware from the respective manufacturers.
- Ran Malwarebytes scan on my computer, nothing found.
- Ran SpyBot and let it have its way with all the things it found. Still have problems.
- Booting and NOT running MS Outlook just now, no problems...
- Opened MS Outlook, problems start.
- Closed MS Outlook... problems persist... end the Outlook task in task manager, no problems... could this be it?
It's hard to say "no problems" definitively, because the problem itself is intermittent. This is headaches.
Do you have any ideas? Potential root causes, or next-steps in troubleshooting? I'm loathe to format and reinstall my programs, but it might have to come to that.
Thank you for taking the time to read my plea.