Problem Activating Themes on Ubuntu

I got WordPress up an running on my Ubuntu server but I am not able to properly install themes. I tried using the automatic installation and manually placing the theme folder in the “wp-content” folder.

In both instances they show up in the WordPress theme manager screen but when I try to “Preview” them only a blank windows comes up, and if I try to install them my blog is blank. I tried three different themes including “Constructor” and “Simpledark” from the WordPress website.

I did notice when I installed the themes the folder permissions were different from the default ones so I “chown”ed and “chmod”ed them to recursively match the two default themes.

Any other tips?