Hmm. It certainly sounds like you got something wierd going on there. Here's a couple of things you can try to see if you can zero in on the problem. Start a new project and digitize a single clip. Lay it in the timeline and see if you can use the Time Remap function. If you can't, then it's likely that the functionality has taken a dive. I would start by trashing your preferences and see if functionality returns.
However, if Time Remapping works in your new project with your new clip, then you may have the far more troublesome "corrupt project, or sequence". If that's the case you need to find out which it is. Start by creating a new sequence in the same project, and laying a clip into it. Try the time remap function. If it doesn't work, try creating a new project and importing some of the clips from your current project and trying the same thing. If it doesn't work then your clips (some or all) are corrupt. If it works, then it's likely your project is corrupt.
Andy