It's hard to say without knowing why it was sandboxed. Try to provide a little more info on what kind of promotion you have done. /Izerman
You need to diagnose what the exact problem is http://www.matthewwoodward.co.uk/tu...acklink-profile-for-current-future-penalties/ Once you've done that you will be able to work out a plan of action. Come on analysing problems is basic SEO stuff, why on earth do you have clients if you can't do this?
I check on http://www.searchenginegenie.com/sandbox-checker.htm and results of my website has been Google Sanbox. I wrote on the forums, create free blogs, but I insert little link. Also I don't know any other reason.