Nanley, no worries and you can not test *every* bug you encounter. Luckily this is one of those bugs which can be easily/quickly tested.
"Should we file this bug to gdm?" - That is the question I'm asking myself too. I thinks it is a GNOME bug, since the GDM window disappears and then the bug appears (so you are actually in the GNOME environment). It could also be a GDM color setting which GNOME just uses, but that is less likely in my opinion.