Memory Leak

I'm pulling my hair out fixing a memory leak in an OpenGL program.  
Don't know if this is related to OpenGL, but I've not gotten any  
takers from IRC. I know the exact line of code that's causing it.

I have a draw function as follows:

draw :: Int -> State -> IO ()
draw autoexit state = do
     clear [ ColorBuffer, DepthBuffer ]

     -- Configure camera and scaling
     loadIdentity
     setView state

     -- Render Cells and iterate
     c <- get $ cells state
     forM_ c (renderCell state)
     c' <- iter c
     -- ==== MEMORY LEAK LIKE A SIEVE HERE ON THIS NEXT LINE
     (cells state) $=! c'

     swapBuffers

-------------

The state is defined as follows:

data State = State {
   frames     :: IORef Int,
   t0         :: IORef Int,
   eyex       :: IORef GLdouble,
   eyey       :: IORef GLdouble,
   eyez       :: IORef GLdouble,
   sphereList :: DisplayList,
   cells      :: IORef Population
}

And the iter function type is as follows:
iter :: Population -> IO Population

The only reason the IO is required is there is a random component and  
I'm using the random number generator in the IO space. If I comment  
out the one line mentioned above, there is no memory leak. The only  
other references to the cells is in the initialization which creates  
the first batch.

garbett:levy-gen garbetsp$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.10.1
cabal list output:
  * OpenGL
       Latest version available: 2.2.1.1
       Latest version installed: 2.2.1.1


It looks like the old data that's in the IORef is never freed. Why  
would this be occurring? Is there a compile flag that would fix this?  
How can I force the garbage collection to free that memory?

My alternative is to use C/C++, and I really really don't want to do  
that.

Shawn Garbett <shawn.p.garbett > at < vanderbilt.edu>
Vanderbilt Cancer Biology
220 Pierce Ave, PRB 715AA
Nashville, TN 37232
Office: 615.936.1975
Cell: 615.397.8737