You are getting the 'Could not open the file' message because someone has deleted the previous Save Game file off your PDA.
Shouldn't make a difference, just click the OK to make the dialog box go away. Tap the screen to start the game then pick Save Game off the Game menu to re-create a new Save Game file.
If you have any further support questions, please leave them in the Forum on the
www.spacetrader.co.uk site.