Empty Trash fails with "The operation can’t be completed because an unexpected error occurred (error code -8003)"

Running a Macbook Pro3,1 OSX 10.6.8

In the trash to be emptied: an OLD Backups.backupdb folder on a Firewire HDD - I bought a new, larger HDD that Time Machine now uses - I'm sure this has something to do with the refusal to empty (i.e. whatever OSX sets on backup folders), which I have never encountered before.

I have tried holding down Option while selecting Empty Trash - fails with the same code.

I downloaded Trash It - but it crashes when I try to run it ⚠.

I tried "sudo rm -ri ~/.Trash" - that completed, and I got excited - but the trash still has the Backups.backupdb stuff in it, and I realized that since the trash in question is on another volume, what I actually need to remove is my trash folder under the .Trashes folder on the firewire HDD. I can't remove .Trashes itself, and I can't list the folders under it, so I'm stuck there.

I could simply reformat the drive in question - and I will if nothing simpler presents itself - but I haven't so far because I have an enormous photo library on the same drive (that's why I want the space back!), I'm reluctant to trust Time Machine 100% to bring it back (even though it is supposedly backed up), and it would take a LONG time to move it to another disk.

I appreciate any advice!