Tamil Font Rendering Problem in Firebox 2

Hi

I am having font rendering problem in firebox 2 alone which is not happening both in IE and firebox 3. I have identified this is due to theme which I am using(Studio Press Green by dailyblogtips.com), because same content works fine in my previous theme (DarkZen from same website). I am strongly feeling its a design problem but I could not identify where to correct it. If you know any solution for this problem please let me know. I am using Tamil (Indic) language in my blog.

Thanks,
Loganathan