Purchased on CO.com
Message from co.com when trying to check in using CO conf#:
We are unable to complete the check-in process at this time. Please proceed to the airport for assistance.
Message from ua.com when trying to check in using UA conf#:
This flight is operated by Continental or Continental Express. If you have not done so already, please visit the Continental website to check in for this flight and any connecting flights, if applicable.
email message from co.com :
You have received this notification because the first flight in your upcoming Continental itinerary is operated by United Airlines and/or its partners.
When checking in for your Continental codeshare flight operated by United, please proceed to the United terminal and check-in area. At check-in, you will receive boarding passes for any connecting segments in your itinerary.
I hate to pass on this news to the traveler especially when it is a busy travel weekend and travelers cannot check in on-line.