Cubase 6.5 Distorting when mastering

I’ve noticed ever since I updated to Cubase 6.5, whenever I try to master my songs, they immediately start to distort.
Example: If I add the Multiband Compressor to the Main Stereo out, even at it’s lowest setting I get distortion.
Same thing with the maximizer.

Before I could add these at their highest settings and I didn’t get any distortion.

I have already trashed my preferences and it didn’t fix it. Is there a setting somewhere that could be causing this?
My ASIO Buffer size is currently set to 256. I tried 512 and it didn’t change anything.

Just before I posted this, I checked the settings in my Focusrite Saffire Pro 40 audio interface, and I tried turning on the “Active Monitor Pad” and that has taken care of the distortion. My monitors are active, so hopefully that isn’t messing up something else.

Update: I just noticed that having the Active Monitor Pad clicked also fixed the distortion issue I was having with VariAudio and Audio Warp.