After upgrading to Prism 3 for Mac, why do I have trouble opening files made in Prism 2?

The creator ID for Prism 2 (IPLT) is different than the creator ID for Prism 3. So when you double-click on a Prism 2 file, the Mac system looks for an application with the creator ID IPLT. If Prism 2 is on your system, it will launch. If you have both Prism 2 and Prism 3 installed on your system, the only way to open a Prism 2 file with Prism 3 is to first launch Prism 3 and then use the File Open command.

If you decide to delete Prism 2, you must also empty the trash to truly delete it. That step is important. If you then double-click on a Prism 2 file, the Mac OS will ask you which program you wish to use to open it. Choose Prism 3. If you then re-save the file within Prism 3, double-clicking on the file's icon thereafter will launch Prism 3.

If you have many Prism 2 files, you may wish to change the creator of these files to PRSM (from IPLT). There are several Mac utilities that do this, including File Typer.