Customers of mine are getting a blank screen when trying to upload banner images or logo images to their templates. Nothing on Apache or SB logs, neither on SB side nor publishing server side.
Ok, got it working! I switched directives "display_errors" and "display_startup_errors" to "ON" in php.ini and got an error message instead of the blank page, saying that a class was not found. I then realized I had renamed a php file belonging to SB in an attempt to fix another error I mentioned in this forum.
Lesson learned: blank page -> turn on PHP error messages!