Microsoft Corp. inadvertently released a pre-release version of an Exchange Server 2007 update that could cause crashes. Update Rollup 4 released to users via Microsoft Update and Windows Server Update Services (WSUS) Microsoft: Issue creates potential for a continuous crashing cycle. Some users reported that they were unable to back up their Exchange servers after installing the rollup during its window of availability. Microsoft did not provide a timetable for issuing a working edition of Update RollUp 4, although such updates would be released on the second and fourth Tuesdays of the month.”]
Source: https://www.csoonline.com/article/2123216/microsoft-issues-wrong-exchange-2007-update.html