A few weeks ago I updated our vCenter instances to 5.5 Update 1a to address the Heartbleed vulnerability. Now Update 1b has been released with further OpenSSL updates, plus host profile and VSAN fixes (blog).
Normally, my update procedure involves extracting the downloaded ISO and installing after that. Today, I decided to simply mount the ISO in the vCenter server running on Windows 2012. That led to my only issue in the upgrade procedure, a problem noted in VMware KB 2050539 but which appears to apply to more than just “VMware vCenter Server 5.1.x”.

In short, the VMware vCenter Inventory Service installer looks for the install files elsewhere (in my case, it appeared to be looking on D:\ while the ISO was mounted on F:\). The solution is simply to copy the contents of the ISO to the local disk and run the install from there.
vCenter Single Sign-On and vSphere Web Client did not have this problem, and since vCenter Server followed my copy to local disk, I didn’t attempt it from ISO to see where it fell on the issue.
Just a heads up to the community.
Great! it solved my problem during upgrade Inventory Service to 5.5.1c
Thank you !!! Just had the same issue , it would be nice if VMware would document this for vCenter 5.x !
Have a great day !
Nice one, had the same issue.
Perfect that solved my problem too !!!!!!