If the list appears where you select a block, the window where you started from cannot be moved. This is due to the fact, that the list you see is actually a separate window as a dialog window. This is why the list can stretch beyond the window boundary (a regular list cannot stretch outside the form boundary - and the real estate is very limited).
Because the second window is a dialog window, one has to respond to it, and once this is done and the window is closed, you can move on as usual. Within the list window you can scroll up and down. You can select one or you can hit <esc> to leave it unanswered. You need to do either one of these to get out of the dialog window, after which you will be able to move the first window up, and open the list again which will be longer because of the real estate available between the box that you clicked on and the bottom of the screen of the monitor.
Note, that listing a block won't fit in the list without the need to scroll. The elements are all there, but if the visible list is short it takes more time to scroll. This - and the fact you need to know the block number, is the reason we also offer the "pick from diagram" option: it switches the focus to the main panel, and if you click on a block there, the focus goes back to the phone conversation, with the block number filled in the box.
The task manager problem would be news to me. If I have the list open (and cannot drag the underlying window) I still can fire up the task manager without problem. Even if the window is so low, that you even don't see the list, just a yellow label "Select now" (which by the way is part of the dialog window), you can bail out with <esc> and the task manager is not a problem (for me).
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