I was in my house when i just dropped dead and when I respawned I was wearing someone elses skin and then I went back and my stuff, which included 7 diamonds had gone.

I can verify that inmate00 had some diamonds on him as we were mining together not too long ago(bout 1 or 2 hours maybe).

It maybe related - I died in a cave with nothing near me at around 5pm GMT or so. Had to relog and run down to grab my things.

These are invisible mobs. It's a bug with minecraft itself, caused when you teleport to a location. Leaving the game and coming back after teleporting makes them visible again.

A relog usually does the trick with you missing items as well.
Many times, they'll be invisible upon return.

I relogged several times and my items still were not there the only thing of value I had on me was 7 diamonds

This drop-invisibility is a big problem for me. It is happening every time. Does anybody know if there is a bug fix planned?

No idea, yet the last half dozen times or so that I've died, I didn't have to relog at all. Everything was still visible.

There has been a recent problem with the grass thinking that its cactus and causing harm to the player but i believe that that problem was fixed