In case that doesn't make any sense...
Adding preview pages to a comic issue doesn't work for my first issue, but I experience no problems with my other 2 issues.
I'm able to select the preview pages by clicking on the check boxes below the page thumbnails, but once I click save, nothing happens. There is no "Changes saved." or whatsoever, unlike my succeeding two issues. When I hit refresh, everything goes back to being unchecked.
Yep, that's basically it.