My guess is that PP just isn't sending out the multicam view.
The Premiere Pro/Blackmagic combo does not work in the multicam mode.
I have both an Ultra Studio SDI and a Decklink Extreme HD and neither ouputs an SDI or HDMI signal to my Sony PVM 2541 monitor when multicam is enabled.
FWIW, my Dell laptop "sends out the multicam view", as Jim put it, via my Matrox MXO2 Mini just fine.
So it's definitely a Blackmagic issue.
I haven't seen or heard yet of this issue. I can output from the Multi-Camera monitor without issue from my Decklink HD Extreme 3D and Decklink 4K. I'll try to test on my UltraStudio 3D as well.
When you say the 'monitor freaks out' what does it do exactly?
Can you provide your system specs and also your monitor model number. Lastly can you include your frame rate and resolution of your media.
Correction: my Ultra Studio SDI now sends out an SDI signal to my Sony monitor in multicam mode. The latest drivers probably fixed this issue but as that wasn't a big deal for me I hadn't bothered to check if a fix had been issued.