[Simulated (OP)]

My high school always had these homemade reeses we could purchase as extras for our lunch. Upon graduation I got the recipe and have made a few batches since. Each time I do as it says, melt icing in microwave spread over peanut butter mixture and freeze. They have been in the freezer for 48 hours and the topping is still sticky!

Is there any scientifical reasoning why?
What can I do so it does freeze?

Thanks in advance,
Simulated

[Geezer]

Put in less vodka.

[CliffordK]

Are you using something like a cake icing?

You might have to post the recipe.  However, I would think you could use something like a fudge recipe.  It has been a while since I've made fudge, but I think we would use a mix of chocolate bars and chocolate chips, and perhaps marshmallows (and nuts & etc).

[RD]

... They have been in the freezer for 48 hours and the topping is still sticky!

Is there any scientifical reasoning why?
What can I do so it does freeze?

The freezing point of sugar solution (like icing) is lower than that of water ...
 http://en.wikipedia.org/wiki/Freezing-point_depression
So can remain liquid at sub-zero temperatures.

http://en.wikipedia.org/wiki/Glycerol#Food_industry
http://en.wikipedia.org/wiki/Glycerol#Antifreeze

[BTW I think icing has to dry-out to harden, e.g. ventilated container at room temperature].

[imatfaal]

My memery of reese's are that they are covered in chocolate - not icing/frosting.  try melting a bar of chocolate in a bowl resting in a pan of gently simmering water - that should resolidify nicely as long as you act quickly.  If you get choccy too hot it will either go manky or refuse to resolidify