Don't know why this works, but it does!! If you remove the bottom plate, take the roller brush out and make sure there's no "gunk" on either side of the roller--you'll probably find lots of dirt, dust and dog hair! Remove that, make sure the belt is tight, then put the roller back. I did this on the recommendation of "Dirt Devil" and didn't see how it would even matter--but it did!!!! Now my vacuum is working just fine!!!!
SusanH, September 2009