Symptoms: When you click on Open Project in SI Text it does not do anything.
Cause: Often times this has to do with the DTL file extension losing its association with System Integrator and more often than not it happens when you load SI 5.5 on a computer that has v4.
Solution: Open your explorer (My Computer) and click on Tools – Folder Options and then click on the File Types tab. Here you will scroll down to DTL and click Change to set the default program. You may see D-Tools System Integrator – Text Version in the list of recommended programs, but if not click browse and go to C:\Program Files\D-Tools\SI 5 and click on DToolsText.exe.