I'm not clear on the symptom you are seeing. Please tell me if this is accurate:
You can start calend normally from the tablet like other graphical apps and use it normally. However, when you use the "Import iCal" menu option it fails in some way. Is that correct? In that case, the most helpful diagnostics for me would be if you attempt the import using "Import iCal". Once that is done, then use the "View Log" menu option and report any error messages in the log that occur after the last "Startup" message.

Starting the app from the command line like you did above should be ok for testing, but it looks like you have become root before doing so. Running it as root is undesirable and should not be necessary under any conditions. The best diagnostics come from the View Log menu option. It's mainly just startup failures like Mechdude's where running it from the command line might be helpful.