Notice [PHP]: Undefined index: nosmiley in file modules/newbb/post.php line 166
Notice [PHP]: Undefined index: icon in file modules/newbb/post.php line 167
Notice [PHP]: Undefined index: attachsig in file modules/newbb/post.php line 168
At least, these 3 sentences is not bug, but only a notice.
I also see the "Thanks for submitting..." box above it, but I'm still not able to see any topic text. This is with the topics I converted over from PhpBB also. I see the topics, but I'm not able to read any of the posts.
Perhaps, the topics converted from phpBB cause some trouble.
As I don't know how do you covert, I can't advise any more.