CERTAINLY YES... Normally you can book capital loss if you sell your investment at a loss. But what about the security / units which are now worthless and no longer traded and cant be sold ? They are still worthless. You cant sell in order to recognize a loss. If you invested in something that is now worthless, you would at least like to be able to deduct the loss as a capital loss.
There is an exception to the general rule that you can't claim a loss on a stock investment until you sell the shares. You can take a loss for a worthless security, which can be unit / stock / bond etc..
I hope this helps...
In that case, I shall opt out and let some other expert assist you.