Can anyone assist?

It is happening to any user that I put in as 'Assigned To' - also i've checked the SMPT server and it is indeed correct. I also tried this Sharepoint Test Email from here (which worked): rodneyviana.codeplex.com/releases/view/19103

Thanks for the suggestion but this didn't work.

I've tried this it doesn't make any difference.

@PaulLeigh - thanks Paul I changed the permission levels for 'Design' and it worked. Any reason why full control wouldn't though?

@PaulLeigh - i'm looking at Site Permissions. Im checking user access via the 'Sharepoint Access Checker Web Part' which shows they don't have full control. Strangely enough thet can have 'design' permissions yet still not amend permissions.

Hi Alexander - the users can't access the user information list.