Bicycle Mechanics - clicking rear wheel

Haro's clicking front reminds me to ask about this clicking in my Ultegra rear. I believe it must be located in the hub and friends suggest maybe the cassett palls. I've had it apart and relubed and inspected the bearings and cassett. No change.
It clicks in cadence with the wheel rotation and stops when not rotating the pedals. I can't hear it when unweighted like on a stand. It even stopped briefly after I had it clamped on a stand a couple days. Usually it hangs by the rims on ceiling hooks for storage. It does vary if I tip the bike side to side, I think decreasing leaning left. Sound familiar to anyone?

Hanging the bike doesn't make any difference, except for scratches on the finish of the rims.

I suspect you might have loose spoke(s). Either your wheel is undertensioned, or you hit a bump, the rim has taken a beating and 1-2 spokes are loose. Pluck the spokes. Those on the right should be very tight, whereas those on the left should be less tight, but not too loose.
Another related problem is that your wheel might wobble if you spin it around.


Basically, true the wheel -- or have it trued -- and it should be ok.

The wheel spins true. I'll check the spoke tension. Thanks

Did you find a solution? My brand new Ultegra rear has the same problem. Two clicks each rotation of crank when pedalling hard, especially out of the saddle. Happens especially when moving very slowly up hills. I thought it was a crank issue but it seems to be coming from the rear wheel. Doesn't happen when coasting or when pedalling on the flat. Could it be the cassette or the hub? Or flexing making the spokes click? Any suggestions from battle hardened click doctors appreciated.