Hi Manuel,
would be good if you could post a screenshot of what you see. Are you targeting the MCF52259? Make sure you assign first the UART. Apart of that, make sure your other components are configured correctly, mainly the CPU with the clocks.
Other than that, if you are using an older CodeWarrior version (the current version is 10.4): there was sometimes an issue that you had to close the project and re-open it again for Processor Expert to get rid of bogus errors.
I hopet this helps.