I haven't used Digital Performer for a very very long time, but after taking a look at the docs a couple things come to mind..
- If you can grab the lines [with the hand] but they won't move, maybe you have the grid set to too large a value [like 1 bar instead of eighth-notes or sixteenth notes]..?
- If you don't get the hand cursor at all, maybe this passage from the DP manual [p.692] could be relevant [particularly the last bit]..
Stretching audio beats in the Sequence Editor
You can also stretch audio beats directly in the Sequence Editor. The procedure is basically the same as described above: choose the Stretch edit layer for the track (see Figure 38-10 on page 380 and “The Edit Layer” on page 381) and use Snap to Grid to determine the span for the anchor points. Also be sure that the Stretch layer is enabled in the track settings (“Stretch” on page 149).
And also this [p.150]:
☛ If you lock the track (“Lock” on page 128) when the Stretch layer is enabled, doing so disables track stretching, as if it is turned off. Beat editing, however, remains available for editing.