Noob needs help with Robocopter upper rotor assembly
 

About a month ago I purchased a Robocopter from a UK outfit (ExtremeFliers) as part of a Groupon deal.

It flew pretty well out of the box, but a bad crash damaged the upper blade set. I ordered a replacement, but here's the problem: I can't get it to attach securely to the shaft. The two screws won't seem to tighten; they just turn and turn. Plus, one of them sticks out a tiny bit, like it's too long for the socket (even though it came out of one exactly like it).

Any thoughts? This is my first time messing with one of these little birds.

Thanks!<br type="_moz" />