Cannot move certain contacts from one folder to another in Outlook

Hello,

In Outlook (2010), what would prevent me from being able to move certain contacts from one contact folder to another?

I created 3-4 temporary folders to use while going through my contact list and doing some sorting. However, I am now unable to move some of the contacts back to their original folder.

For example, one temporary folder contained about 145 contacts. I selected all of its contents and dragged them to the main contact folder. However, after doing so, 23 contacts still remain in the temporary folder and I cannot find any way to move them.

I tried dragging one at a time, I tried right-clicking followed by selecting Move, I also tried copying to paste (but that is not given as an option) and I've made sure there is not already a duplicate file. Nothing pops up such as an error message but it just does nothing at all.

Any ideas regarding what the problem might be?

Thanks