Yeah, happened to me as well. Was level 30, got back to level 1 from one match to another.
In fact I don't really care, but it's quite weird and should be corrected.
i also experience that problem. was reset once i reached lvl +20. until yesterday i was like lvl 33 again and after starting an arcade map from within the sp (arcade-poster) i was resetted again
Me too. I was playing both the campaign and Arcade. The campaign quit on me (no error message, just returned to desktop) -- that might have had something to do with it.