Plug the USB from the Raven directly into the computer if using a HUB, ff that doesn't help, try a different USB cable.
Be sure the correct touch driver for your type of Raven. Raven MTi1 uses Multi Touch Platform and Raven MTi2 uses UPDD. If Multi-Touch Platform is installed on an MTi2 system, be sure to un-install Multi-Touch Platform then re-install the correct MTi2 installer.
If MTi2, open the System Tray from the Task bar and click on the UPDD "hand" icon and check "Status", is it set to handle monitor 1????
Also, be sure UPDD TUIO is showing in the System Tray in the Task Bar, as this is where Raven gets its touch info from.
Double check the computer is seeing the USB device SIS HID Touch Controller, if this is not showing then there could be a USB port issue.