Well, after much deliberation I bit the bullet and replaced the hot-shoe on my D700. For well over 6 months I was having issues with misfiring of my SB900 and couldn't work out what was causing it. I cleaned the contacts, I made sure I had freshly charged batteries in the flash, but just couldn't get to the bottom of the cause. After a Google search, it appeared that the problem is not uncommon and most of the recommendations were to replace the hot-shoe. I got a quote to do this - AUD220 with me supplying the hot-shoe that I purchased on line from the US (I had visions of grandeur that I was going to replace this myself - yeah right). The replacement of the hot-shoe involved also having to replace the front rubber grips on each side of the body. Not a cheap exercise but I didn't know what the other alternative was.
The strange thing was that my SB800 worked fine on my D700 - never misfired! Even stranger, my SB900 never misfired on my D300. I could have gone on with the combination that worked but how frustrating is that, not being able to use your SB900 on your primary camera.
So had it done today and tested it the same way I did previously and so far so good - no misfires. Happy days (I hope I'm not being premature here). I gotta tell you, the replacement rubbers certainly give the camera a nice new look and feel
In anycase, hopefully this helps others who may be having similar issues and deciding whether its worth doing. Happy to answer any questions for others having similar problems.