Can’t Get to Dashboard

I uploaded to WordPress 2.5 and now I cant get into my Dashboard. I get this error:

Warning: require_once() [function.require-once]: Unable to access \./admin.php in /var/www/vhosts/puntabulous.com/httpdocs/wp-admin/index.php on line 3

Warning: require_once() [function.require-once]: Unable to access \/admin.php in /var/www/vhosts/puntabulous.com/httpdocs/wp-admin/index.php on line 3

Warning: Cannot modify header information – headers already sent by (output started at /var/www/vhosts/puntabulous.com/httpdocs/wp-admin/index.php:3) in /var/www/vhosts/puntabulous.com/httpdocs/wp-includes/pluggable.php on line 689

My website is https://www.puntabulous.com (but only puntabulous.com works, if you put the www there it doesn’t work. That’s another problem).

Any help would be appreciated!