Unable to view categories in Admin area

I have a problem that when I click on the Categories/Products link in admin that my browser will not display anything.
I have tried different browsers and all are the same.

Any help would be greatly appreciated.

Do you have any Add-ons?

What has changed since the last time that you could see the Categories?

I am not sure.
I migrated the whole site to a new server, all was working fine.
Today I went to the site and SEO was causing errors and I cannot view categories. I have disabled SEO.

Are you able to see other things in the Admin such as Customers and Manufacturers?

If you browse your database tables:
categories
categories_description

in phpMyAdmin on your new site, do you see the data?

If you look at your two configure.php files:
/includes/configure.php
/admin/includes/configure.php

do all the paths, database, username and password match correctly?

I have checked all paths and they are correct, all other fields in the control panel work without error.

The product details show correctly on the site. I am just unable to edit or add products as I het a blank browser page.

Did you try to just reload all the files for:
/admin

and all subdirectories and their files?

Sounds like you have a bad upload or some file corruption ...