Occassionally the ActiveState.com site goes down, and it's not unheard of for them to temporarily rearrange things in ways that break PPM. But the error you're getting is wierd. What, exactly, are you typing to leads to this error?

By the way, I don't see XML::Sablotron in the ActiveState packages repository (http://www.activestate.com/ppmpackages). You may need to install it manually.