Okay, so I'm upgrading my Drupal site and get the "White Screen of Death" when I run update.php. Of course I start sweating thinking "Oh my Gaw! My site can't be updated and I won't be able to add content and people won't see it and what's going on!"

Just for the record, last time I added content to my site was...
So you see why I'm in a panic.

Anyway, after lots of emails between myself and my web host's tech support I still had a white screen, but I knew that my site was running PHP5 and how to use phpinfo.php to check that, although in my control panel PHP4 was still showing.
I had initially believed that the AddHandler in my .htaccess to force use of PHP5 was the issue since when I removed it I was able to run update no problem, but PLEASE don't make me downgrade to PHP4 after I've been using PHP5 for more than a year!

Putting my cyber-embarassment aside, I finally gave up and posted in my web host's forums. It's not like it's a stupid question, right?
Well, the help I received was well intentioned, but honestly I had no clue why I was checking file permissions or further more why I had no errors in my logs (at least pertaining to this issue, the really old error from December I kind of...never knew about).
I also posted in the Drupal forums, again hoping I wasn't "thrashed" for not reading the 2 million forum entries on the white screen topic (by the way I did read and A LOT. However, every recommendation failed with me or did not pertain to my error).

The reply was the same as the last one I received from tech support stating my memory was too low and the script could not execute. "Check the settings in php.ini." Upon reading forum topics I'm advised that the php.ini file is the appropriate place to increase this, however, .htaccess and settings.php can also be used. I know I have increased the memory in ALL of these files so I am totally confused.

So, I figure I will recheck this only in php.ini (deleting the increase memory line in both .htacces and settings.php) and increase the memory until I get the script to run. Well wouldn't you know it, I increased the memory to 372MB and still nothing. What? How can that be? What the heck?

I'm not sure, but I happen upon another post with a one liner update something like "changed MB to M and it works." I figure I've tried everything else, why not.

I'll be...! It worked! I'm able to run update.php no problem, no white screen and using PHP5!

How did I get away with using MB for so long in php.ini? Odd.

Hopefully I've saved someone a day or two of screaming at the computer.