I know what you are talking about, It happened to me once. check out this thread, about half way down I explain how to take it apart.
but I left out how to fix the creeping, after you take it apart take a socket (I use a 11mm put it is a standard size) and unscrew the brass nut you can now see. The brass nut (has an o-ring on it), a spring, a small rod, and a black disk will fall out, pay attention to how they fit together, it is not hard but you will need to know for when you put it back together. The black disk is causing the creeping. Clean it off and flip it over and put it back together. Just hand tighten the brass nut back on. If that doesn't fix the creeping you need a new disk which you can order from the palmers web site. If you have any more qeustions, just ask.