Restore problem

K this is a intermittent concern. It has happened a couple of times to me today. I have been bouncing between 2 roms tweaking and customizing. I want to delete some old backups that I will never use to free up some space. Sometimes when I go to restore through nandroid it will kik me back to the menu saying something like no such command and unable to mount sd card then reboots my phone. I thought I had it figured out cause I was in Astro in my backup section renaming backups and I just went back home. So I went back in and exited all the way out and it allowed me to restore. Now I am stuck on this rom and unable to restore back to old roms to make sure I want to delet. Any help would be appreciated

 

Haha yeah o am on a milestone. So far I have flashed 3 different roms without a hitch (knock on wood). I only had the restore problem twice. I do everything with rom manager or clockwork.