VMware vSphere 5: Private Cloud Computing, Server and Data Center Virtualization
913577 is actually the client build.
923238 is the vCenter build.
So it would make no sense when you updated vCenter to a client build. Maybe you are already on the correct vCenter build?
Can you have a look in the vSphere client, in the menu bar in Help -> About VMware vSphere and possible get a screenshot if the build number really is below 923238.
Careful there are 2 build numbers in that pop up, one for the client and one for vCenter.
