We updated one of our Citrix XenApp servers and this message started flooding our Application event log:
“The winlogon notification subscriber <TrustedInstaller> was unavailable to handle a critical notification event.”
So what’s going on here?
Examining the registry on a ‘good’ working system and the ‘bad’ system revealed the following:
How did that value get there?
It turns out we installed Internet Explorer 11 with our patch cycle — but that in and of itself did not cause our issue. Additional components for IE 11 were installed as well:
“Microsoft Windows English Spelling Package” and “Microsoft Windows English Hyphenation Package”
Neither of these packages are present on any of the ‘working’ systems. I tested to determine which of them placed the registry key there…
It turns out both of them do. If you uninstall *either* package it will remove the ‘CreateSession’ value. Since these packages are not in our standard build we are removing both.