Getting blank pages

Hello

I am using wordpress 2.3. The wordpress is installed in http://www.domainname.tld/blog on a zeus web server.

Below links are directed to above url using .htaccess file.
http://www.domainname.tld
http://domainname.tld

.htaccess file have just this
ErrorDocument 404 /blog/
ErrorDocument 403 /blog/

Few days ago i upgraded wordpress to 2.3.1 and aftr that below url is showing just a blank page.
http://domainname.tld

http://www.domainname.tld, and http://domainname.tld/blog and http://www.domainname.tld/blog works ok.

If i change the blog url from admin interface to domainname.tld/blog then http://www.domainname.tld start showing blank page.

I tested a new installation of wordpress 2.3 with above setup and it do the same.

Anyone have any idea please ?

Regards

James