I upgraded a few weeks ago from 2.1 to 3.1 of the theme.
I know that version 2.1 of the theme worked on a Blackberry Bold (9650, OS 5.x ) a few months ago. I had to make a fast change to site while on the road and I used the wife's BB she has from work.
Just on a whim I went back to the site again from the same BB and all you get is the title block area with the logo icon, the site title and slogan, everything else is white. No text or pictures. I tried another Drupal site that has a fairly old theme that is table based, and it worked just fine. I even tried a different BB, again a Bold 9650, slightly different version of the OS and a different service provider.
Doing some research it seems that newer version of the BB OS, 6.X is about out that has a completely revamped web browser in it that is based on webkit.
There is a BB simulator that can be downloaded to see what the browser does, but that wouldn't help in determining just what part of the theme's CSS is confusing the BB browser unless someone wants to do a lot of trial and error work.
One website reports that the BB browser treats overflow: scroll and auto as hidden. Maybe this has something to do with the mostly blank screens.