VPN/Remote Desktop Connection Disconnecting

I am having a problem staying connected to my office VPN. I can connect without a problem but after approximately 2 minutes, the connection fails and then reconnects. This happens like clockwork, every 2 minutes.

I am running Windows Vista, a wireless laptop, a D-link wireless router and using SonicWall Global VPN 4.0. All Windows updates have been installed as well.

Does anyone have any ideas as to why this could be happening? I’ve already tried changing firewall settings and that didn’t help.