Samsung Galaxy S stuck upgrading firmware. Should I unplug my phone? Should I keep on waiting?

I tried to upgrade my firmware on my Samsung Galaxy S using Kies The Firmware upgrade appears to have gotten stuck. Kies says Upgradeing firmware... Do not disconnect a mobile device from the PC during upgrade process Progress Bar has "Upgrade is in progress.." and is stack at about 1/3 The phone screen shows a green triangle with Downloading... below it and "Do not turn off Target!!! at the bottom. It has been this way for about an hour. What should I do? Should I unplug my phone? Should I keep on waiting? I really don't want to end up with a brick.