I am also having this problem trying to get hellopod_orange on my site. The standard hellopod theme works fine, I just want to try out the different color scheme.
My current setup is:
System > Design. Set to default/hellopod according to the instructions: http://www.hellothemes.com/support/documentation/hellopod-documentation/
Removing this or changing it to default/default breaks the site.
System > Configuration > Design > Skin. Set to hellopod_orange. This is with the ‘Default Config’ Current Configuration Scope selected. ‘Main Website’ and ‘Default Store View’ are set to Use Default.