Just seeing where you are based, it's not ideal
Aside from the above suggestions.
First thing I'd go and do - bed the pads again, do it properly.
Various methods but here is a good one - do it obviously in a quiet, no traffic place:
http://www.350z-uk.com/topic/18649-how-to-proper-brake-in-procedure/
If you still have the problem, these are things you can do at home:
Remove the wheels, ensure the rear surface is totally smooth and completely flat, free of any paint.
Also the hub where the discs sit, this should also be free from corrosion/dirt etc - so give that a quick rub with sanding paper.
After that, it's best to ensure the wheels are weighted properly, and then I'd have the discs skimmed.
Have a look at my thread here:
http://www.350z-uk.com/topic/97748-marcus-disc-skimmers-excellent/