Backing up a partition to disk image unmounts that partition

[dnanian]

It sounds to me like you're using the 'imaging' option in the Options page rather than saving to an image by choosing it in the 2nd pop-up. They're quite different (and the one in Options is device-specific) -- I suggest not doing that, and I think you'll be OK.

Also: rather than using *either*, I'd suggest using the method detailed in "How do I update an image?" in the FAQ. By using a sparse image that way, you'll be able to update it with Smart Update, rather than having to create the whole thing from scratch every time. (There's more on this topic on p21 of the User's Guide -- take a look!)