Cache problem - Go to a page once, but not twice

I have the Cache enabled and set to a 5 minute lifetime. When I log out > then access any page as Anonymous > then try to access that same page again (even a Refresh) > I get a blank page (no errors displayed or logged). Then I'm kind of trapped because I can't go Back or go to any other page I've visited before.

It's gotta be a problem with the Cache somehow or the information sent to it. If I disable the Cache - no problems. If I monitor the Cache in PHPMyAdmin > delete the visited page entry > access the page one more time - no problem. I want to use the Cache though! :-)

I have two installations of Drupal to monitor. On my main one, the one with this problem, I have many modules and customizations. On the other installation, my secondary, I have no modules or customizations. On the secondary I cannot produce this problem so it leads me to believe it's all my modules and customizations right? So I disabled everything that I thought would affect this - no success.

I've attached my SQL dumps for the Cache from the broken site and from the working site. Also a screenshot from PHPMyAdmin showing the entry (for the user/register page) I can delete and make things work one more time. These little bad boys are the problem! (internally somewhere)

I am hoping that someone knows how to analyze this information and can find the bug. Or has anyone else ever had this problem? Any thoughts would be greatly appreciated. Thanks in advance :-)

_/03