Hmmm what a mess!
First up Gilles, it certainly sounds like the issue you are having is because of the function theme_enable_block_region, or more accuratly because the you've also copied anomaly's lib.php and PHP is erroring because the function now exists twice.
In this case the solution is to CVS update, that function was no longer being used within the anomaly theme and should have been removed long ago! (MDL-25028)
If you cannot CVS update (or don't know what that is) you will need to wait for the daily/weekly build of head. In the meantime you can delete the function from your theme's lib.php file which will fix the issue immediatly for you.... you should do that anyway actually.
In the future any functions within a theme should always contain the theme name so that when people do copy a theme and just replace the theme name everything still works. I'll add that to the docs shortly.
Now as for Tim's comment about overriding the theme instead of copying it and Mary pointing out that the readme specifices otherwise.
This is an interesting issue, I've been thinking about this for a couple of minutes and too be truthful I do, and always will create themes which override, and never duplicate a theme. Why, because otherwise I will have to watch any changes to the theme I copied as well as perform general maintenance on the theme I created.
Yes, if the theme you are overriding changes dramatically you will need to fix up your theme. However you will get any bug fixes in the original theme, you will get styles for new areas, and the chances of big changes after release are very slim.
Personally I see overriding as much less work, and much more reliable than coping. Yes, you will need to perform maintentance every now and again, but your theme will more likely work in later versions of Moodle and likely won't require as much attention.