No cite for my specific claim, but I found this Engadget article claiming MS's Entertainment & Devices Division (read: Xbox) was $80 million in the black in 2008:
Are we looking at cumulative Xbox profits from day one? Generally one is interested in a division's ability to generate positive cash flow, no matter the initial cost, because it's assumed that division will generate said cash flow in perpetuity.
http://www.engadget.com/2008/01/24/xbox-goes-profitable-almo...
Note that I got the write-down year wrong--it was 2007.