Just managed to clean up my partners site (well I think I have) following some of the pointers in this thread:
1) .htaccess had been appended to with “Error 404” directives. Removed those only.
2) Removed sm3.php and wp.php completely.
3) Updated thumb.php to the latest version from https://timthumb.googlecode.com/svn/trunk/timthumb.php which has hopefully closed any holes.
This seems to have solved the issue and I’m not seeing any redirects to the .ru site anymore.
Note: I have not scanned the DB yet.