yes... I'm aware of the graphics problem, but I still don't know what is causing it (it not happens with pharo 1.2 or squeak, so I think is a combination of "something" in vm side -cocoa version, that "something" in pharo changes brought to front). I will work on that some time this week :)
In the near future, the only version of cog vm should be cocoa version, but there are still some remaining issues who prevents ppl to adopt it (not very big issues, and there are a lot less issues now, but still some remain). I think one of the main reasons is that both Eliot and Igor are working on the carbon version, not the cocoa one (for historical reasons: cocao version didn't exist when Eliot started working on Cog). I would love to join those efforts and drop carbon version (which is legacy), but I don't think it will happen any time soon, sadly :(
This are the issues preventing people to adopt cocoa version (at least those I can see now):
1) Not enough plugins. This is SOLVED, currently, hudson builds came with almost all the plugins provided for old carbon versions (4.2.x)
2) No MacMenusPlugin. Still there. Not a big issue, as we can live without them, but it will be nice :)
3) This annoying graphics problem... I hope to solve it soon.�
4) I didn't release a 6.0 stable version (because of the graphics problem, now) :)