Help with Blocks and Themes

[ITFS]

I really like the block setup on my forum, but every time I try out a new theme, the left and right blocks dissapear.  I've gone through the Admin panel and they're all still Activated, but they aren't there.  Do I have to modify the theme somehow, or is it just stuck like that?

Any advice would be Very helpful,
ITFS

[H]

Please provide us with a link to your site and which themes you have tried