Problem with mr SkyPortal through solid window glass object.

[Nanne]

Hello mates, my first post here. I'm in need of some mental ray expertise :)

I'm trying to render this interior scene with large windows looking outside. The exterior background is a photo mapped onto a cylinder. I'm using the Daylight System and a mrSkyPortal to direct the light to the inside (Multi: 5.0, Shadows from outside, Sampling: 128). The window glass is made out of two solid meshes, two sheets of glass that is.

The problem is I get this ugly noise in the windows and these white dots here and there that looks like bad reflection/specular highlight calculation but it isn't. I've isolated the problem to be the SkyPortal, here are two test renders - with and without the SkyPortal.

With SkyPortal:

http://nanne-san.com/files/helpfiles/Interior-KitchenCamera-01.jpg
Without SkyPortal:

http://nanne-san.com/files/helpfiles/Interior-KitchenCamera-02.jpg
(I rotated the environment cylinder in the second render to get a better, less dark, background view, that's why the backgrounds looks different.)

Any tips on how to fix this? :)
Cheers!