Possibly a NAT issue?

[Achromatic]

I'm running a Cisco VPN client -cringe- (though i've tried with vpnc).

Secure shell sessions often disconnect repeatedly, and sometimes every few minutes, though sometimes lasting for hours. I know the connection isn't going down (or rather, if I SSH to an outside server NOT using the VPN tunnel, and from there via VPN, that connection stays up)…

"Semaphore timeout period has expired" is the error I get (from SecureCRT).

Other relevant details:
Vista x64, Realtek 8168B gigE, using Realtek drivers, not MSFT, version 6.214 (current, or very nearly).
Comcast cable - business connection, using static IP addresses, MTU 1500

Any thoughts on where to go from here?

[glor]

I found that my PPTP vpn connections were doing this also, I went into the System Advanced settings and checked the box for:
Disable Firewall Scrub