Since always.

The changes that an update makes to your system can be misinterpreted as
virus-like activity. In addition, most antivirus programs incorporate script
blockers. If your antivirus program is active during the installation of an
update, the update may fail and your system may become unstable.

From Microsoft's Windows Update Troubleshooter:
"Make sure you have disabled any ad removal programs, Web accelerators, and
anti-virus programs prior to accessing Windows Update. These can cause
script errors."

Rocky