Don't know if this is useful, but running 270.41.19 with 126.96.36.199 kernel on amd64.
free with most everything shutdown(X and most unrequired daemons)
total used free shared buffers cached
Mem: 6114788 3769372 2345416 0 440 1462240
-/+ buffers/cache: 2306692 3808096
Swap: 7802876 44 7802832
Attached is a log from kmemleak. Don't know what took the ram though 3.7 gigs is alot for only what was running at the time.
I'll try to reproduce.