We really don't recommend driver level passwords. If that sector of the hard drive is damaged, the password will be damaged and access to that data is lost unless a data recovery service is used.
If using FWB HDT Primer to password protect the drives, there may be some corruption keeping you from accessing the data. Check for damage and test the drive. The drive will need to be reformatted, because there's no way to get around the password if the volume is inaccessible.
If using a 3rd party application to password protect the drives, give them a call and see if they have compatibility issues with PowerMacs or with FWB software. There may be another way to get past the password.
Machines Affected: All