Contact Adobe Tech Support. They'll deactivate the installation for you so that you'll again have two available.
For your convenience, please use the following online Adobe Chat (for activation/deactivation) link to ask Adobe to take care of the trapped purchased activated serial number on crashed computer. It is the only one who can help you in this type of situation.
If you are currently getting the "too many same purchased activated serial number" when you go to install on a 3rd computer, I would expect this should be a quick and effective process. If not, then it is Adobe's call on if it will help you.
Please let us know the outcome as your schedule permits.