Updating iTunes 12.1 and get error message "The procedure entry point CMBlockBufferCopyDataBytes could not be located in the dynamic link library CoreMedia.dll - what went wrong and how to resolve this?

Question

Updating iTunes 12.1 and get error message "The procedure entry point CMBlockBufferCopyDataBytes could not be located in the dynamic link library CoreMedia.dll". What went wrong and how to resolve this?

Answer 1

Entry point errors can often be fixed by deleting the offending dll, then repairing the component it is part of.
For general advice see Troubleshooting issues with iTunes for Windows updates.
The steps in the second box are a guide to removing everything related to iTunes and then rebuilding it which is often a good starting point unless the symptoms indicate a more specific approach. Review the other boxes and the list of support documents further down the page in case one of them applies.
Your library should be unaffected by these steps but there is backup and recovery advice elsewhere in the user tip.
If the advice above doesn't resolve things you could try this alternate version:
iTunes 12.1.0.71 for Windows (64-bit - for older video cards) - itunes64setup.exe (2015-01-28)
which is a 64-bit installer for the 32-bit version of the core application, similar to previous 64-bit releases.
Or roll back to the previous build:
iTunes 12.0.1.26 for Windows (32-bit) - iTunesSetup.exe (2014-10-16)
iTunes 12.0.1.26 for Windows (64-bit) - iTunes64Setup.exe (2014-10-16)
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