Diskdoubler files corrupt?

[kfinkler]

help! I've been trying in vain to open files that were compressed in DiskDoubler. I've tried running Classic and opening in DiskDoubler 4.1 as suggested in this thread. Disk Doubler

I get an error message "An error occurred ... Checksum failed" - this has only occurred recently, I used to be able to open the DD files in Classic mode, but now I get this error on trying to expand almost all old files. I've tried renaming the files, I've tried Stuffit, I've tried 'the unarchiver'.

any suggestions?