When I first upgraded to Vista I had a horrendous time with network copying issues. The new networking stack in Vista was different to XP and caused lots of problems. For many people local copies to and from servers seemed to be the issue, but for me it was copying files over a VPN.
This VPN link worked fine with XP to the remote W2003 server and would copy large files (say 8MB) without problems.
Vista had a problem, and it appears that the fault lies in the router or possibly in how Vista tries to optimise the file copy, which would essentially reset its connection half way through the copy and re-establish it. I never managed to fix this and even the SP1 fixes didn’t change this situation.
Now I have a Win7 beta running on VPC I’ve just been testing this over the VPN and to/from local servers and things look like they are a LOT better. In particular the VPN copies do not seem to cause restarts on the router/VPN so it looks like Microsoft has spent a bit of time on this area.
Looks like I was fooled by something, as it does not seem to be fixed. The problem is I cannot identify where the issue lies – at the router or Vista/Win7. I suspect it’s a problem with the router but this is difficult to pin down.
Worse still I’ve found that even when I use the inbuilt dial-up VPN within Vista similar problems are happening with large transfers. I will set up a Win7 RC client on a test machine and see if it is still there.