Shouldn't this be in technical help?

One possible solution:
Open up My Computer
From the Tools menu, select Folder Options
Click on the File Types tab and scroll down to whatever .J2I is called
Click on it, then click Advanced
under Actions, double-click on Open
Make sure %1 (under "Application used to perform this action") has no quotation marks around it

Can't remember if I did this for J2I files or not, but it worked for something Jazz-related.