Yes, it's a problem. Doesn't matter whether the united.com view of the reservation sees the space confirmed -- the operating carrier view of the reservation needs to show the space is confirmed.

Can you view the reservation on Air China's web site? When I have booked Air China award space I have been able to use Travelsky's web site ( http://www.travelsky.com/tsky/ ) using
* the United eticket# or the Air China PNR (call CA for it if you don't see it on united.com view of the reservation); and
* various forms of the passenger name exactly as they appear on the eticket (LAST/FIRST for someone named First Last or sometimes LAST/FIRSTQMR for someone named Mr. First Q. Last, or experiment)

CA ticketing should not take a long time. Call UA and CA tomorrow and ask them to reconfirm the space is held; if CA says the space is not confirmed, call UA and have them fix it ("CA says the space is not confirmed in their system, please fix") and if necessary hold a three-way conference call (I have never done this).

The language to use with a UA phone agent tomorrow (if needed) is something like "Hello, I made an award booking online yesterday and the ticket was issued, but I called the operating airline to confirm the reservation and they said that the itinerary was not fully confirmed. Can you please contact them and help resolve this problem?" You don't necessarily want to give a phone agent TOO much info up front -- this can confuse them, especially if you're not exactly right about the details.