You say you are using FTM2012, but then you talk about "Save This Person to My Tree"...???
"Save this Person to My Tree" is the lingo if one is going to merge a person into your ancestry tree.
FTM's Web Search Workspace has no such button and uses the little green arrow in the lower right corner.
I'm confused with what exactly your problem is. I've been using FTM's Websearch to merge records (although I have to admit I never merge people) all week long with no problems.