The shutdown script in usermode-1.36-2.6.x.i386.rpm calls /usr/sbin/shutdown, which does not exist. All occurences of /usr/sbin/shutdown should be replaced with /sbin/shutdown, which is in the SysVinit-2.78-5.i386.rpm package.
Please check if the usermode-1.37-0.6 package in http://people.redhat.com/nalin/test/ fixes this. Thanks!
Yup. The usermode-1.37-0.6 package in http://people.redhat.com/nalin/test/ does fix this.
We'll be pushing this out as an updated security fix today. *** This bug has been marked as a duplicate of 19034 ***