Loosing referral id in referral link registration

[nirvana43]

Hello
I have problem with referral link registration on my forum.
If i follow link like : http://www.mydomain.com/register.php?referrerid=34 or any referrerid,
it takes me to accept/agree forum rules step in registration process. At that time its showing link as http://www.mydomain.com/register.php?referrerid=34
But when i click Agree to forum rules, it takes me to http://www.mydomain.com/register.php?do=register and it does not put referrerid in field. Instead its putting first member i.e. Administrator or referrerid=1 name in referrer field of registration form.
Can any one tell me what could be wrong?

I didn't installed any mods on my forum which can possible mess up with referrals.

Edit : User Referrer system is ON in admincp
Kinda same problem this guy faced : https://vborg.vbsupport.ru/showthread.php?p=1207022

--------------- Added [DATE]1250564321[/DATE] at [TIME]1250564321[/TIME] ---------------

BUMP!!
Any one?