To answer my own question for others that may run into this same problem. I'm using logical volumes (lvs) from LVM to back the disks up in RAW format. The source and the destination have to have matching sizes; due to an accounting error they didn't. The error message didn't make it entirely clear what the issue was but I'm glad it has been resolved. Hopefully others will see this message when searching for the same text I was searching for and will check the lv sizes on the source qemu instance and the destination qemu instance.
Thanks again, Abe
