[wp-pro] help! themes and permissions

[Tony Kelly]

i'm a rookie at wordpress, and our wordpress site,  
potreroboosters.org, can't seem to activate its theme.

this was a problem for months, and kept me from updating the site.
i finally upgraded to 2.3.3, and loaded the following themes:
Big Blue 0.1 (that's 'current')
WordPress Classic
WordPress Default

they are all in the wp-content/themes/ folder.
the images for the themes show up on the theme page at my dashboard,  
but ...

obviously they don't activate on the site.

and then i tried changing folder permissions, and ... now the whole  
site is down.

i'm probably missing something really obvious, but ... what is wrong??

can someone help me clean up this small mess?

thanks

Tony