One - have you applied all updates?
Two - For Windows (not sure about Mac but may help)
Work through all of the steps (ideas) listed at http://forums.adobe.com/thread/459220?tstart=0
If your problem isn't fixed after you follow all of the steps, report back with ALL OF THE DETAILS asked for in the FINALLY section at the troubleshooting link
Ensure that you have targeted a track" for the insert or overlay to function from the shortcut keys."
Welcome to the forum.
I think that Craig's Track Targeting will be the key to the Insert Edits.
As for the PageUp/PageDn, they will ONLY work if the Timeline Panel has focus, i.e. the yellow/orange border around it. This is how it works, but can "get you," if you have been working in other Panels, and one of those still has the focus. Happens to me, when I am in the Effects Panel, and do not shift my focus back. Just click anywhere in the Timeline Panel (or use the keyboard shortcut) to give it focus.
Thanks everyone - I think that clears things up...much appreciated!