I have activation type for new user set to "activation by administrators". The problem i have is with the email that is emailed to the admin. The link is only:
/forum/modules/profile/activate.php?op=actv&id=2&actkey=dceadf24

It lacks the domain of the site.

When I add the domain of my site before it, I get the following errors:
Notice [PHP]: Use of undefined constant _US_YOURACCOUNT - assumed '_US_YOURACCOUNT' in file modules/profile/activate.php line 71
Notice [PHP]: Use of undefined constant _US_ACTVMAILOK - assumed '_US_ACTVMAILOK' in file modules/profile/activate.php line 76

Can anyone tell me where I have gone wrong?