Ah - that may be different then. I'd imagine your problem will lie in whether the shares were disposed of/the loss realised before or after the CGT gain. If you haven't actually disposed of the shares, then the advice in my first post would remain the same - you'd have to try with Revenue to see if you can elect to write them off as of a date before the gain (or in the same tax year) and then you should be able to offset that loss.
For example, if you were doing it all now and hadn't made any losses or gains yet, I'd do that procedure whereby you can write off share values when they are essentially worthless, then offset the gain in the same tax year against those losses. The wrinkle is whether, if you haven't disposed of the shares, the revenue will let you make a retrospective election to write down the value of the shares. The point is not necessarily whether the shares were worthless as of 2000 (when they would have allowed the write-down), but whether they will allow you do it now.
I'd write to them and explain the share history, telling them that the shares were essentially worthless as of the date the company went into receivership (2000) and that you inadvertently neglected to include that against a future capital gain.
Note that, if you do receive money from the liquidator in respect of the shares in the future, that will be treated as a gain on the entire amount if you have chosen and are allowed to write them down to zero now.
Good luck with it
Sprite