+2  A: 

This is likely a loss of focus where switching between Excel and PowerPoint is causing PowerPoint to lose focus and therefore there is no ActiveWindow for PowerPoint to paste in to or the ActiveWindow becomes a different Pane in PowerPoint, such as the Slide Sorter or the Notes pane.

Otaku  2010-07-16 18:03:25
@varient: Got it. I'll have to try to replicate the issue before offering any advice. Give me a while for that - I'm in Hawaii right now :)
Otaku  2010-07-16 19:46:29
@Otaku - Thanks, Otaku. Please post your "Loss of Focus" message as an answer so that I can credit you the points on this one. You were bang on. The solution was to add a line telling it to re-select the main window. It looks like it was going to either the slide sorter pane or the notes pane.Application.ActiveWindow.Panes(2).Activate
variant  2010-07-16 19:52:39
@variant: got it, good to hear the issue was discovered and fixed. I've changed the answer above.
Otaku  2010-07-16 19:57:32

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