Alan Holbrook wrote:

Several times a year, my computer response time plummets like a
wounded robin, and usually at the same time, I can't seem to start
some of my applications. Either nothing happens at all or else I get
a few seconds of the hourglass followed by nothing at all happening.
I finally noticed, after this happened several times, if I click on
the 'Start' icon and then on the power icon, I see the little orange
dot and the message 'Update and restart' or 'Update and shut down',
depending. When I click on one of them (usually 'Restart'), the
machine goes through its usual couple of centuries of 'Do not turn
off your computer' and finally completes the update and the restart.
And surprise, surprise, when that's all done, my computer is running
at its normal fast speed and all my applications start normally. So
does this happen to any of you, and if it does, do you have any idea
of why the system behaves the way it does when updates are pending?
Or is this just another example of Microsoft being Microsoft?

Unless you have hidden it, the Windows Update Status tray icon will
appear when an update is either pending to install or a restart is
required. If you elected to hide that icon (by default it is shown),
then you'll have to click the up-chevron at the left end of the systray
to show the hidden icons, or go into the taskbar settings to elect NOT
to hide that tray icon.

When updates have been partially applied, there is a mix of new and old
files. The old files cannot get replaced until a restart of Windows.
Until you get the entire fileset in sync for a feature, the behavior of
that feature is undetermined. I just had an update of the .NET
Framework libs, which means a restart was needed to get its entire
fileset in sync rather than a program trying to call .NET functions with
indeterminate results while the .NET fileset is a frankenjob mix.

When a restart is needed, you can see in the Windows Update panel just
what update is pending a restart. You didn't mention what update was
awaiting a restart. You said all applications were impacted, but it
unlikely you actually started every application currently installed on
your computer. Knowing which applications were affected might hint as
to why they are impacted in common. However, usually knowing what was
the pending Windows update that required a restart is a better target
for diagnosing the trouble.

This is an example of a user ignoring a restart. You would expect a
prompt telling you a restart was required, but that doesn't always
happen. In addition, some users disable the restart prompt: Settings -
Update & Security - Windows Update - Advanced Options - Update
Notifications (enable it to see a prompt that a restart is needed after
applying an update, so you'll see the tray icon to alert you). In fact,
some updates do not specify a restart is needed in their manifest, but
the result can be a hodegpodge of old and new files for a particular
feature. It is safer to do a restart of Windows after any update to
Windows, even if not told a restart is required.