Okay, so I was working on a project just now, imported a new MP3 in as an asset, and then suddenly, something disastrous that's happened to me before has happened again - the clips won't slide into place automatically. Meaning what? Well, whenever I move one sequence/clip by the side of another in the Timeline section in the past, the clip would normally lock into place automatically, preventing me from making the clip overlapping the one I'm sliding beisde. There will be, like, this white line thingy when I hover one clip over other clips to show me the beginning and the end of each clip in the Timeline. But now it's gone! It's missing! It's... disastrous! I must've pressed something, but I tried resetting the Workspace and reopening Premiere CS4 and that auto-slider still doesn't reappear!
Try the Snap icon in the upper left of the timeline or press S with the timeline active.