Visual Editor don’t work after upgrading to 2.3

I was using 2.1 and i just upgraded to 2.3. But after I upgraded the Visual Editor is not working properly. I can’t click on the empty box to start writing a post. But the space for the Title works.

At the status bar it shows that page is downloaded but with errors. And the error is as follows:

Line: 184
Char: 290
Error: Access Denied
Code: 0
URL: http://www.mysite.com/blog/post-new.php

I’m using Internet Explorer 6 (which didn’t give me any problems previously with the earlier version)

I tried to redo the whole upgrading process a few times already. I even deleted everything and started fresh but the problem still persists.

Can anyone suggest a solution? Or should I revert back to an earlier version like 2.2?
Or is it the Internet Explorer, or my local PC?

Any help is appreciated.