What versions of FastChip & the softmodules are you using?
What software tools are you using?

Are you sure you've connected the UART softmodule's Tx and Rx to the correct physical pins on the device? Beware: you can close the FastChip IO Editor with unsaved changes and it will not warn you!

Are your Bind, Generate, and Configure up to date?

Are you sure that you have the baud rate, etc, etc correctly set up (most terminal emulators are likely to display "junk" characters with incorrect speed and/or framing).

Do you have a polled or interrupt-driven UART driver?

Although I haven't built it myself, Application Note AN03: Using the Interrupt Expander Library Module uses UART softmodules.
The supporting files are available via the Support Centre at:
http://portal.knowledgebase.net/utility/getfile.asp?rid=1360