Thank you, that put me on the right track. btw, a better way would be to point your Virtual Host "External App" config to $SERVER_ROOT/fcgi-bin/lsphp5 (instead of lsphp).
Some old tutorials from before when Litespeed buildscripts supported PHP5 told you to just replace the default lsphp with the PHP5 binary you built by hand. Apparently I have been running a PHP5 from dec 8 2007 all along, only with new PHP5 script-libraries. Whoops..