Unable to add Users after upgrade to 6.1.0

[Brendon74]

Sugar Version Version 6.1.0 (Build 5389)
Sugar Edition Community edition
Category admin/usermanagment
Operating System centos
Database MySQL
Web Server . Apache

After upgrading to 6.1.0 from 5.1.0. ( a long and not so easy process). And then moving to a new set of hardware. Everything is now working as far as my old data being there including all custom forms etc.

BUT when i try to add a new user i get this response:-

Server error.

The website encountered an error while retrieving http://***.***.***.***/sugarcrm/index.php. It may be down for maintenance or configured incorrectly.

I have searched and searched and i can not find a resolution for this.
Please help.

Reagrds

Brendon

[andopes]

Do you have custom fields on Users module?
Do you have access to error log of apache?

Cheers