'The operation is not supported error' when trying to create a backup on USB drive

I am booting to an Acronis USB boot disk and then selecting to backup to another USB drive. I use this method successfully on various laptop/desktop models from Dell. This is not working on a new desktop that I have received - Dell Precision T1700. As soon as the operation begins 'The operation is not supported' box pops up. I have tried different USB flash drives, I have tried formatting to NTFS, FAT32, I have changed which USB ports I am using and it is still not working. Firmware is up to date on the desktop as well.

Any thoughts?

Acronis True Image 2015 (build 5539)