OK, I think it works now after being brave and resetting to factory defaults. I had not changed anything and it was working only recently, so I don't know what happened... Now I just have to change a few things back to have it as it was before resetting and then it should all be fine. I cannot wait to observe the nebulae you have mentioned. I just got my nebula filter the other day!
PS: I realize a nebula filter is for nebulae, but some people say they also see more stars. I didn't, maybe because it is not a large scope.
It is a Celestron filter, and it should work fine with a 5" scope, and even a 4" one, but probably only for nebulae:
http://www.celestron.com/astronomy/c...r-1-25-in.html