misaligned block returned

Hi!

I tried to pass a big heap to a program and get the following error:
getMBlocks: VirtualAlloc failed with: 8
main: internal error: getMBlocks: misaligned block returned
    Please report this as a bug to glasgow-haskell-bugs@xxxxxxxxxxx,
    or http://www.sourceforge.net/projects/ghc/

That happens even for a "Hello world" program. The border is 1956M.
So +RTS -M1956M -RTS is fine. +RTS -M1957M -RTS yields the error above.

PS: I know that is a big heap and I could probably do with less when I track
the space leak down, but at the moment it is not worth the effort. I only
need a single run that passes. (With probably 2.5 - 3 GB memory usage.)

PPS: Please cc any answers to me because I am not subscribed to
haskell-glasgow-bugs.