Can I deauthorize a computer that is no longer working or crashed?

If you've got 5 computers authorised for the account in question, and you need to free up authorizations, I'd do a "Deauthorize All" from one of the computers you have access to, and then reauthorize the computers you have access to.

For instructions, see the following document:

iTunes Store: About authorization and deauthorization

This is not an acceptable solution APPLE needs to fix this..... they have no problem gathering our computers information to authorize a computer they need to allow us to pick from that list of authorized computers and deauthorize them.