OS X :: 10.6.2 / Dock Icons Disappearing And Moving?

I have been trying to figure out why my MBA seems to be so odd?

I am running 10.6.2 OSX and every time I try to move the icons around in the dock they either move place by themselves or delete themselves?

This is especially true with browser icons. For example I could have safari open and try to move the icon in the dock from the far right towards the left ..... It will do this and stay there for approx. 5 seconds and then return back to the far right.?

If I close the safari program the icon disappears from the dock. If I then try to drag the safari program into the dock from the applications folder, it will sit there for 5 seconds again and then just delete itself off the dock. This also happens to Skype, Firefox etc.....

I have tried everything from terminal / killall Dock ..... to deleting files from /Users/~/Library/Preferences/com.apple.dock.plist etc with nothing working ??

// ps I do have a mobileme account with syncing function but have dock syncing turned off etc .... I have also tried re-booting multiple times after trying different routes and nothing has worked.

After trying nearly everything I can think of (even checking repairing in disk utility) I seem to have drawn a blank.

So I have enclosed a video of my desktop showing the problem of the disappearing icons. The weirdest part is its selective so some icons could stay when being dragged their while other disappear in a matter of seconds?