Can't install modules, blank screen - linux permissions??

From the install new module page, every time i try to upload a new module tar (or same behavior trying to FTP) and after the post back all i get is a blank screen. The module never gets installed.

I'm hosting my own site. I've used Drupal on other paid-for-hosting sites and I've installed modules that way so I know what the intended behavior should be, I'm just trying to learn how to do my own web hosting.

I've tried switching in the drupal config to use either /tmp or {drupal root}/sites/default/files and I can see my uploaded tar with permissions -rw-rw-r--. So I was wondering, is it a permission issue where the apache user (www-data) isn't able to untar the file? There's nothing in my apache error logs that would indicate this though. I've tried completely opening up my web folder (777) and experimented setting the sticky bits and stuff but no luck there. I've tried setting a variety of owner/group combinations: root/ww-data/my user, etc... but still no luck.

I am completely stumped why I can't install new modules through the web interface. I know I can always do it manually through the command line but I really want to figure out this environment configuration issue.