As has been said back in 2007..

Like itar said, it is likely no good anymore, though if you've never opened it before.. there might be a chance it is still good.
In this case you should wonder whether you could miss your mould form and the masters, if so, feel free to try.. if not, well, still your choice on whether to try it or not.
If the goop doesn't set solid in a couple of days, I'd just bin the form masters and all, I wouldn't try salvaging lego or masters.. uncured goop is a real pain to remove from stuff!