Error getting UID/GID

[Terry]

I get this error using vexim which is a php front end for exim ( I have 
mailed there list )
I am running it in a jail and when I goto add a new domain I get Error 
getting UID/GID.
All existing domains and accounts are fine ( these come from another 
server and have been moved into the jail ) and I can add users to 
existing domains with out a problem.
I get the same error with apache or lighttpd. All joomla sites are 
working fine so I assume every thing is ok php wise.
Nothing gets shown in the web server logs.
The uid and gid are set in variables.php but you can also change them if 
you wish when adding a domain
I am just wondering would it be some sort of jail related issue ? But I 
can not see a sysctl that it maybe

 sysctl -a | grep jail
security.jail.jailed: 0
security.jail.mount_allowed: 0
security.jail.chflags_allowed: 0
security.jail.allow_raw_sockets: 0
security.jail.enforce_statfs: 2
security.jail.sysvipc_allowed: 0
security.jail.socket_unixiproute_only: 1
security.jail.set_hostname_allowed: 1

7.1-RELEASE ,PHP 5.2.8 (cli)
Just looking for some pointers where to look really

Thanks
Terry