After cleaning my filters my filter wheel started doing all sorts of crazy things. On power-up it would stick between filters or select a random filter to settle on. When I tried to move it it would slowly chug past each filter. In a panic I emailed Chris (sorry for those emails, Chris) before I thought to open the wheel up. I discovered that there was a small notch in the o-ring running around the wheel. This was probably caused by my not correctly removing or reinstalling the wheel. Naturally, since the gear engages the rubber, a notch or other imperfection on the rubber is bound to cause problems in registering the wheel filters.
I turned the rubber around so that the notch faced inward. Problem fixed. The morals: check that rubber for imperfections if acts funny and make sure to completely retract that gear when removing and replacing the wheel. Naturally, the latter is exactly what is stated in the EFW2 Manual.
Ed