Similar here (to this and a lot of posts). In my case the story may be a little bit illuminating in a different way, though. My OP account was my main account, but after I status matched/linked my MP account I flew all my United flights using the MP number as it bumped you up slightly in the upgrade queue (example: me as gold last year using my MP Premier Exec # beating out my boss at platinum using his OP # once). The last couple of years I have been about 1/3 UA, 1/3 CO, 1/3 US biased slightly in that order (so a little more UA, little less US).

So, as it happens this year I have not yet flown any "Continental", but the US Air I have flown (~6000 miles) went to my OP account. All of my US activity is showing up. I have flown about 13k miles UA including three segments last week. Two of last week's segments are showing up, but none of the rest of my UA activity this year is (to the tune of 10k miles or more).

My guess has been that something just needs to run in batch to fix the UA miles, except maybe my missing segment last week which I had expected to be hosed up since that whole flying experience was hosed up due to a blizzard.

Oddly though, my number of segments is showing up as 20.5, which sounds about right...

Now that I think further, the bit about not having flown "Continental" could be wrong. My missing segment last week was a 50 seat RJ that departed from the former CO gates of SLC to SFO. That could be PMCO maybe? SFO to LAX on an Airbus is certainly PMUA, and that is showing up. Strange. Ah well. I don't think I am flying for the next two or three weeks, so with any luck all this dust will have settled by then.