Sudden “require_once” error

no idea what happened here but suddenly got this error msg when trying to use wp

Warning: require_once(/var/vhosts/babble.cheggit.net/html/wp-content/themes/k2oem/app/classes/sbm.php) [function.require-once]: failed to open stream: No such file or directory in /var/vhosts/babble.cheggit.net/html/wp-content/themes/k2/app/includes/sbm-stub.php on line 21

Fatal error: require_once() [function.require]: Failed opening required '/var/vhosts/babble.cheggit.net/html/wp-content/themes/k2oem/app/classes/sbm.php' (include_path='.:/usr/share/php:/usr/share/pear') in /var/vhosts/babble.cheggit.net/html/wp-content/themes/k2/app/includes/sbm-stub.php on line 21

the obvious thing is that it seems to be trying to refer to both k2 and k2oem themes. i’d be more than happy to change the theme but i can’t use the system.

sudden is the right word. nobody has been in the installation for weeks (last modified on the dirs says so) and i haven’t posted in a few days.