Did you follow instructions in download section in garage ?
Preference doesn't have to be edited. Default value are ok.
If you do so remove /home/user/.streamtuner directory and install streamtuner again to initialize correct default values.

Streamtuner is declared beta only because
- menu are not hildonized
- fullscreen is not implemented
- some cleanup need to be done in the menu (epiphany, etc ...)

But Streamtuner work quite well on nokia 770.
Just follow carefully installation instruction.

If you still have problem, use dedicated forum on garage to ask help.