I have quite new a nice machine I also record in Reaper. I use HD500X via USB.
I have had similar issues. I did everything I found on forums (windows optyzmiastion), along with reinstall of windows. Still suffered from random crashes. I get me so pissed that I even started to think to stop recording music.
Finally I started to work by myslef and used self powered USB HUB, it helped a bit but problem was still there. After all I decided to try another USB interface (focusrite) all my problems are gone...everything works like a charm.
What comes to me after all of this (nearly two years...) that POD is good for gigging and practicing, but it is not stuff for recording - when time will come for new equpiment I know that L6 is not part of the deal.