Vista RDP disconnect issues – disconnects from internet

Objective:  Connect via RDP from a Toshiba Satellite L550 with Vista Ultimate SP2 and RDP 6.0 to a newer Shuttle XPC with Windows XP SP3 and RDP 6.0

Issue: RDP connects, but immediately or shortly thereafter hangs and disconnects.  Internet connection is also affected, dropping down to “limited” with no access.

Background: Brand new laptop.  User has 3 year old Toshiba Satellite with XP SP2 that works flawlessly for the objective described above.  New laptop was connected to a backup Cable internet pipe on an SMC 8014 Broadband Gateway with an ethernet cable and tried to do an RDP connection.  I could get connected, but it was dropping the connection almost immediately, staying connected only a minute or two with activity before giving up and disconnecting.  Not only that, but the entire Internet connection would drop and I’d be left with a “limited” connection.  Interesting.

Things I have run into when dealing with Vista and the Internet:

1. uPNP is often a problem when interacting with Vista networking.  I have had limited success disabling it on a router to ensure that I stay connected to the router.

2. Vista AutoTuning.  Several articles online advise setting the Vista autotuning to “restricted” or even “disabled” to workaround connection drops when dealing with Vista-NonCompliant routers and devices (including Cisco firewalls and Sonicwall appliances).

3. IPv6 – There’s a bit of buzz online about disabling this, but I’ve never run into a situation where it made a difference. 

I tried all of the above, but nothing worked.  Finally I came across a tool from Microsoft that helps you to analyze the capabilities of your router (or other network device attached between you and the internet).  This is specifically useful for troubleshooting Vista connections:  http://www.microsoft.com/windows/using/tools/igd/default.aspx

Results:
uPNP = NOT SUPPORTED
Multiple Simultaneous Connection States Test = NOT SUPPORTED

I hooked the laptop up to another network (Linksys RangePlus-n WRT110), but this time wirelessly and RDP worked fine.  Analyzed that network and saw this result:
uPNP = NOT SUPPORTED
Multiple Simultaneous Connection States Test = SUPPORTED

A third network (Linksys RangePlus-n WRT110) also worked and it too supported MSCS.

On the surface it appears that the MSCS Test is the crucial one.  

UPDATE:  Cable company upgraded the firmware on the device.  Did not fix the issue.  They came and installed a dynamic modem in place of my SMC.  Now when I connect it gives me a partially black screen.  I think I saw the fix for this on the internet somewhere. I’ll research tomorrow.  Sigh.

Things I can try in the meantime:
1. Attach a compatible wireless router to the Cable Modem and connect wirelessly.�
2. Upgrade the laptop to Windows 7 and hope it works better.
3. Downgrade to Windows XP because I’m pretty sure that will work.