I'm using a PPTP VPN connection in OS X to connect to my work. I've had this working fine in the past on other Macs, but on my white Intel 24" iMac it seems to want to constantly send all traffic over the VPN.

This option is disabled in the network settings, however whenever I'm connected to work, I can't do anything else like browse the web, etc. I've enabled the option, and applied, then disabled and applied, all with the same result.

Any ideas? I've even recreated the connection a few times.