SuperDuper vs. Finder Drag and Drop?

[sgmorr]

I use SuperDuper, and love it, to maintain a clone of my iMac's internal HD on a peripheral Firewire HD. I have the FW HD partitioned and use one partition for my Clone and another for bulk storage. I backup my Pictures folder and some music and documents to bulk storage even though they are also backed up in my Clone. On occasion, I have just dragged and dropped my User Library folder to bulk storage and it has worked fine. But today when I try to do this, I get an error message (error code -8072) saying that an unexpected error occured and the operation could not be completed.

Is this an error with Finder? How should I go about getting a copy of my User Library into my bulk storage partition (I know I already have this copied safely in my Clone partition)?

Thanks.