Ok, so it looks like it should be looking for the top and bottom fileman frames at:
'/home/webmail/data/admin/templates/fileman/blank.html'

instead of :
'/home/webmail/data/admin/templates/blank.html'

At least that's where the fileman templates seem to be.

Line 432 of admin.cgi seems to be pointing to the right place for the fileman templates. This is starting to make my brain hurt.

seaturtle.org