realpath error

I’m using Buddypress and uploaded the appropriate files and activated the plugin only to get this error whenever I now try to access sections of the site admin.

Warning: realpath() [function.realpath]: Unable to access /var/www/vhosts/xxxxxxxxx.org.au/subdomains/brainstrust/httpdocs/wp-content/uploads in /var/www/vhosts/xxxxxxxxx.org.au/subdomains/brainstrust/httpsdocs/wp-includes/functions.php on line 2058

this, I assume is because the actual url should be httpsdocs as in line 2, but I have no idea how to change it – or where, can anyone advise??

Dee