I made some chocolate ganache this morning (a recipe I found on here http://cakecentral.com/a/chocolate-ganache-2 ) and it won't set up enough for me to whip. It's been in the fridge for almost 5 hours. Any suggestions as to why it won't set?

You should never actually let it cool in the fridge, you want to let it set at room temp, in the fridge you're going to end up with unstable fat crystals. The slower it cools, the more stable it will be.

You could take it out of the fridge and see what it does in an hour or two, but generally speaking there is nothing you can do for a ganache that hasn't crystalized properly.

It will probably harden up eventually in the fridge, but the texture will be off.