Originally Posted by
petrolhead
A bit of a long shot, but my bike did exactly the same last week. The next ride the the rear derailleur cable broke right at the shifter lever. Turns out the cable was frayed internally, preventing the shifter from pulling the cable all the way to precisely shift the largest three rear cogs.
this sounds very possible, or something similar, especially since the OP stated that he had just changed the cable and housing...