1. Highlight the entire group, copy it, paste it into excel. Use destination formatting (or text import wizard, and make sure the text qualifier " is unselected or you'll lose all your phrase matches).
2. Turn on autofilter.
3. In the keyword column (or whatever column helps you sort the results), try to figure out a custom filter to determine what keywords you want in the new group. This will save you a lot of time if you can figure out a combination.
4. Hightlight and copy those results into sheet two.
5. While these words are still highlighted in the first sheet, use clear contents.
6. Goto show all all results (or reverse your custom filtering, if you used 'don't show words that contain - then use 'show words that contain)
7. In sheet one, copy and paste those keywords back into your original group.
8. In sheet two, copy and paste everything into the new group.
9. Make sure you preview the results and that it looks correct before saving.
10. If you use power posting, it might take a bit of finagling to make sure you have all the ** in your sheets, but you should be able to copy and paste the URLs & bids back into the groups and have them saved properly.
In the latter case, I'd suggest a simple copy/paste. Just go to the 'Edit Keywords' link in the 'old' Ad Group, copy the keywords that you want, then paste them into the keyword entry box in the 'new' Ad Group.
Then, as Syzygy mentioned, delete the keywords in the 'old' Ad Group, if you haven't already done this during the 'copy' step.
BTW, the ability to do this more simply has been forwarded as a product suggestion.
AWA