Exchange 2000 Upgrade problem

During an Exchange 2000 upgrade from 5.5, we received this error message:

One of both of the Microsoft Eschange 5.5 Information Store databases was determined to be in an inconsistent state.

If we cannot quickly resolve this problem, we would like to go back to the original 5.5 configuration.

Can anyone either resolve the error message or if not, lend advice on reverting to the original configuration? Thank you.