Kan niet meer in de admin

I am not exactly sure what my version is (forgot sorry) problem is, i had moved a site from a subdomain i use for testing to the original site hosted somewhere else. Well that didnt work for the first time so i moved i deleted that one.

Now at my test site i cant acces the admin and i didnt do anything about that site!! This is the error i’m getting:

Warning: Cannot modify header information – headers already sent by (output started at /home/deb7280/domains/hogebrug.com/public_html/budgetbuddies/budgetbuddies/wp-content/themes/twentyten/functions.php:1) in /home/deb7280/domains/hogebrug.com/public_html/budgetbuddies/budgetbuddies/wp-includes/pluggable.php on line 890

Does anyone know how to resolve this?

Regards Bas