iTunes upgraded to 12.3.3.17 now failing continuously

Such errors can usually be fixed by deleting the offending dll, then repairing the component it is part of from the programs and features control panel. JavaScriptCore.dll is part of Apple Application Support and can normally be found in

C:\Program Files\Common Files\Apple\Apple Application Support or

C:\Program Files (x86)\Common Files\Apple\Apple Application Support.

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.

The further information area has direct links to the current and recent builds in case you have problems downloading, need to revert to an older version or want to try theiTunes for Windows (64-bit - for older video cards) release as a workaround for performance issues or compatibility with third party software.

Your library should be unaffected by these steps but there also links to backup and recovery advice should it be needed.

tt2

I'm having the same issue. I tried deleting that file and repairing Apple Application Support and I got an error that iTunes was not correctly installed.

The 12.3.3.17 release seems to have a problem with proxy configuration scripts. It may be best to roll back to the last build of iTunes that worked for you. See iTunes installers for download links. If you're rolling back from 12.3.3.17 to 12.3.2.35 then you'll also need to roll back the library database in the way described in Empty/corrupt iTunes library after upgrade/crash.

tt2