Comment 10 for bug 408603

Bug is still an issue here. I have found a work around for those who still have issues.

Extract the tar.gz file into a folder foo.
Hit ctrl+h to show hidden files/folders
Open the .evolution folder.
Copy the backup-restore-gconf.xml into foo.
highlight the 3 item now in the foo folder.
Right click and select compress.
Call it evolution-backup.tar.gz.
Now direct evolution to the foo folder and the new evolution-backup.tar.gz file.

Magically it now works.