ok here go's first look on every page to see if you have more than one <h1> then if thats all ok make sure all pages have different title+ descriptions ect and then pray
How old is your site? Its its pretty new, then its normal. Otherwise, and if it is really sandboxed, you need to find the reason. If you give us the url we may help you.
Google is looking for websites that offer quality content, make sure that you always write quality content post for the site. And you need to wait. The sandbox filter is not a permanent filter and is only intended to reduce search engine spam. It is not intended to hold people back from success. Good luck