Unable to add cookies, header already sent.

[musclediscussio]

I just migrated my server to a new one different os version but rest of the environment is same.
I moved all my accounts using cpanel account transfer. Now i am getting strange errors

Only 1 light theme seems to be working right now when i try to view the forum category it shows

vBulletin Message
Unable to add cookies, header already sent.
File: /home/muscledi/public_html/includes/config.php
Line: 1

If i modify the cookie prefix to md instead of bb it gives me a different error which it shows if i select some other theme.

Fatal error: Call to undefined method stdClass::set()

Please hellp