I am testing on the dev release 0.7
I would like to install the database without the bf_ prefix.
if you try to remove the prefix, the install fails with the message
There was a problem saving the backup file.
once I removed the prefix it worked.
I think the error is probably unrelated to the prefix. I.e. it worked for you the second time simply because it was a second attempt. I predict that if you tried re-installing the same site, you would be able to remove the prefix.
I didn't manage to reproduce this error myself, so it's difficult to figure out why it happens. However I did see it once before your report. I wasn't trying to remove the prefix, and the error went away when I retried. (I didn't recopy files or anything, just went back to the first install page and redid the install).
Ooh... it was worth looking up the error text though. There's some suspicious path code there. Also note that if you're struggling and need an immediate workaround:selecting the modern 'mysqli' database driver instead of 'mysql', will currently bypass the code that generates that error.
Fix installing with mysql db driver (issue #753)
Gotcha. I didn't fix the path to work in the installer, I just realized that a fresh install doesn't need to backup the Bonfire users table half way through the process :). (Migration of an existing install should be unaffected).