It was the first of Microsoft's monthly updates to include minor enhancements to its major software products as well as security updates.
MS14-045 applies to Windows 7, Windows 8, and Windows 8.1, plus Windows Vista and Windows Server 2003.
While the update has installed without difficulty for many, some reported system crashes and problems restarting their systems.
The reason this problem did not show up in testing is because it only happens under specific circumstances, Paul Ducklin wrote in a Sophos blog post.
The fault is triggered only on systems that have one or more OpenType Font (OTF) files, installed in non-standard font directories, that are recorded in the registry with fully qualified filenames.
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Ducklin notes that a default Windows 8.1 install, for example, includes only TTF (TrueType Font), TTC (TrueType font Collection) and FON (Windows bitmap FONt) files, recorded without pathnames.
Microsoft has published a workaround to help Windows users up and running again, but it involves a “fair amount of fiddling,” according to Ducklin.
As well as MS14-045, three other Microsoft updates may cause this problem. Microsoft has removed the download links to these updates while these issues are being investigated.
Ducklin said anyone who has installed these updates should remove them along with Ms14-045 (2982791) in step 7 of the workaround published by Microsoft.
“Unfortunately, and understandably, Patch Tuesday aftershocks of this sort leave sysamdins wondering if they should approach future updates more cautiously.
“We regularly urge you to ‘patch early, patch often,’ so let's hope Microsoft's patch for the broken patch goes smoothly, lest even those who weren't affected this time get cold feet next month,” he wrote.