Just discover this problem while taking a training course. My Ripple Delete shortcut is not working. I did a mark in and a mark out on a section in the timeline and attempted to do a Ripple Delete which the command should be Shift + Backspace. It will work if I go to the Edit drop down and select Ripple Delete. I also checked the Keyboard Customization and it is ok. I also did a test on the Edit drop-down list and did a Ripple cut which is Ctrl Shift X which shortcut did work which is the same thing. At least it worked the same way. Any suggestions?