It's always a bit frusterating when you can't figure out what the problem is - as drupal continues to improve there are more and more tools that can tell you how to target an issue or determine where the issue was originated (like the theme developer module see: http://www.drupal.org/project/devel ). There is also the amazing FireBug addon for firefox which I could never live without.
Today I came across an issue that I couldn't track down - nothing would show up in the status logs and I didn't have access to the server logs which left me in a tight spot. A blank white screen.
Thanks to a brief post on the whydrupal.com blog that suggested adding
to my settings.php page located at sites>default>settings.php where my site is installed. Midway down the settings file is a list of variables that start with "ini_set". You can simply add that little snippet below the others.
Once I refreshed my screen I discovered that my page wasn't loading because I didn't have enough memory allocated to do so. That's a simple enough fix (see this page for help: http://www.journeymm.com/blogs/drupal/maximum-file-size) and away we go!