Cannot copy to partition on boot drive?

[riwi]

Previously I have successfully used SD to copy files between both partitioned and un-partitioned drives. Today however, in the "Copy" drop-down menu, all of my drives and partitions are listed (both internal and external); in the "to" drop-down menu, the identical list appears, but one partition (of the internal boot drive) is grayed out and cannot be selected. All other drives and partitions are selectable. As per recommendation elsewhere, I deleted the Saved Settings folder, and restarted with external drives turned off, but that one partition remains grayed out. All partitioned drives have been partitioned as GUID.
Are files not allowed to copy onto a boot drive partition via SD?

[dnanian]

You can't copy to the drive you're running from: you could end up causing some severe problems that way.

[riwi]

Thanks for the info!