In some cases, simply booting using the recovery CD can correct what ever the problem was. In other cases it will allow you to get logged into winodws. If you can get that far, it will be much faster to decrypt from within the operating system.
If the recovery CD is unable to get you logged into windows but it does accept your passphrase, I would suggest attaching the drive to another computer (using an external drive enclosure). If pgp is installed on the other computer, you can then use some of the steps/options in the knowledge base.
(As far as decrypting using the recovery CD, one customer reported it took 8 days.)