BrynS has found an interesting item at FiringSquad. It's a mention of Chris Roberts in an article titled What's Killing Game Development? which suggests that back-room dealings lead to his departure from Digital Anvil in 2000:
With the exception of Will Wright, few of the any old, great designers have done much lately. Sid Meier's name is on a bunch of games, but it's not actually Sid in charge of development or design. Chris Roberts, of Wing Commander fame? Let's just say he had a conflict of interest with the Wing Commander movie and his projects at Digital Anvil, and that Microsoft's sudden, detail-free take-over of Digital Anvil has quite a few details if you scratch beneath the surface.
Roberts left Digital Anvil in December, 2000. The announcement came in the same press release which reported that the studio had been sold to Microsoft. This quickly followed earlier rumors that Roberts had been removed. Microsoft had previously been an equity partner in Digital Anvil and was then rumored to be unhappy with the amount of resources Roberts had spent to finish the Wing Commander movie.