First, in Ubuntu, try going under System -> Administration -> Hardware Drivers. Your particular card may be supported, but it might not have free (meaning open source) drivers. Ubuntu aims to be fully free out of the box so you have to manually go in there and enable the driver.
If that does not work, we would need to know what chipset your card uses. Please post the output of:
And when you post that, if you could, "Go Advanced" in your reply and wrap the output in the code tags - highlight the text and click the # button, just makes things easier to read.