I've only tried spectator mode once (yesterday) and it went ocmpletely black and then logged me out. When I tried to log back in, it said i could not connect to the server.
After completing the misison, it went to the summary page and then everything froze. Then it went funny. The summary was on top of the log in page but I couldn't click any buttons. So I had to force quit.
It happened again. Everything froze and I couldn't click anything. I was leaving the treasure vault in T2 by the elevator
here's a screenshot
http://i596.photobucket.com/albums/tt44/JennytheTurtle/spiral%20knights/...