if you're on win 2k/xp/Vista, look at a cli proggy called 'route'
I've never used a vpn and dunno the specifics, I have used multiple gateways on the same PC tho, so,
I'm guessing that you...
either end up with two local subnets (ie 192.168.1.x your real local, and 10.1.1.x your vpn)
or end up with one bigger subnet local and vpn (ie 192.168.1.1 the vpn gateway and 192.168.100.1 your local gateway)
in either case your vpn gateway might somehow be becoming your primary gateway, which is the source of the problem.
if it's something like that you can lookup your NSP's server IP (might be multiple) (hint, on a CMD enter: nslookup news.blahblah.net)
(optionally) if it's a single ip then change your altbinz config to the IP instead of the domain (ie instead of news.blahblah.net x.x.x.x)
then use
route add x.x.x.x your.local.gate.way
route add y.y.y.y your.local.gate.way
(I suggest you add this to a batch save it somewhere and then add a 24h task for it in windows tasks, cause the routes seem to get wiped every time the line resets)
where x.x.x.x and y.y.y.y are the IPs of the NSP server(s) add as many as you need if it's multiple.
if no internet traffic is supposed to pass through your VPN you might wanna spend some time tweaking this batch so that all internet traffic goes through your local gateway and not the remote (vpn) one. and only permit vpn specific traffic to pass through the vpn.
don't take any of the above for granted that they are correct in respect to VPNs, again I haven't used a VPN (neither software nor hardware based) and I dunno the specifics.