Thanks for all the responses. Called MH earlier today. The original e-mail advising of the change didn't provide a reason, but the call agent advised the change was due to "technical reasons". The agent advised that a change to Cathay Dragon wouldn't be possible without charging a fare difference....of 4,000 MYR! I inquired if I could change to the morning MH flight, fly in coach (no business seats available), and receive a credit on the original fare....and was advised this would not be possible. The MH agent did advise I could make a change to a different date at no charge, and ultimately I decided to fly out a day earlier. Although a bit disappointed I couldn't change to KA, I now have an e-mail from MH confirming the change to the earlier date and with a seat assignment, so I'm good to go.