Ditto on the tax issue.
Unpaid tax liens are particularly onerous. In addition to being a major derog, they have the unique distiction amongst reported adverse items of information of not being excluded from your credit report after a period of time that is pegged to the occurance of the adverse action itself.
Unpaid tax liens are pegged to the date of payment of the tax lien, and thus the 7 year clock does not even start ticking until paid.