Firstly, if you have invested money in the company, is it one on which seed capital relief can be claimed?
If you haven't been paid by the company and won't be, you will be entitled to tax back for this year but this won't be repaid until you submit your 2007 tax return.
Alternatively, if you have a tax credits cert issued in relation to your employment by the company, you could have the company pay you a small sum in December and the company would repay you the tax (and reclaim it from the Revenue).
If your tax affairs for the previous years were in order and you claimed anything you were entitled to (medical expenses etc) you are unlikely to be due a refund from those years.