Bangla Fonts Rendering No Longer Work After Upgrading to SnowLeopard

I have recently upgraded to Snow Leopard (10.6.2). But my Unicode Bangla/Bengali fonts rendering no longer work. In particular, rearrangement and substitution do not work. These same fonts (AAT based) used to work on 10.5.x without any problem. Now I get ইউনিজয় instead of ইউিনজয় .

I tried to validate the fonts from Font Book. But it shows the following:

'cmap', 'hmtx', 'loca', 'post', 'sfnt', 'head', 'hhea', 'maxp', 'glyf', 'fpgm', 'prep' -> all ok
Duplicate fonts -> ok
System Validation -> ok
'name' table usability -> (minor problem)
'name' table structure-> (serious error)

I trashed Font Book preference and re-installed the fonts, without luck. Any ideas what I am doing wrong? Is there anything wrong with the fonts themselves?

Thanks in advance for help.