Originally Posted by arterture

It could be that it only does it under load. When I spun my crank without the chain it wasn't very noticeable but it wasn't spinning as well as it should have been. I actually put my ear up to the frame when I spun it and I could kind of hear a sort of crunching/grinding noise. Ended up being water in the BB which was causing the bearings to go bad.

This may not be your problem but it's something to think about if you only notice the problem when you are pedaling.

Originally Posted by KevinF

Chain lube and grease aren't the same thing. Just about any type of grease will do; your local hardware store will probably have some, or your LBS will be happy to sell you some as well.

Note that your pedals (since they were installed without greasing the threads) could be nearly impossible to get off in the future unless you go back and re-install them with the threads greased.