bug in squeak 4.2/4.3 Cog/non-Cog

i :=1.
myRectArray :=Array new:10.
rnd := [(-500 to: 500) atRandom].

    myGrid := PasteUpMorph new openInWorld.
    myGrid height: 1100;width:1100.
    aRec := myGrid center.
    myRectArray at: i put: RectangleMorph new.
    1to: i do: [:count|  myGrid addMorph: (myRectArray at: count)].


    [Transcript show: (Time millisecondsToRun:[
        1 to:1000 do: [:j|
            1 to: 1000 do: [:k|
            1to: i do: [:l| (myRectArray at: l) center: aRec +(rnd value@rnd value)].
            ]]]);cr] fork.

"++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
myGrid delete.
Smalltalk garbageCollect.
"++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
i :=2.
    myGrid := PasteUpMorph new openInWorld.
    myGrid height: 1100;width:1100.
    aRec := myGrid center.
    myRectArray at: i put: RectangleMorph new.
    1to: i do: [:count|  myGrid addMorph: (myRectArray at: count)].


    [Transcript show: (Time millisecondsToRun:[
        1 to:1000 do: [:j|
            1 to: 1000 do: [:k|
            1to: i do: [:l| (myRectArray at: l) center: aRec +(rnd value@rnd value)].
            ]]]);cr] fork.