Front end freezes on start-up

The only solution I have found is to delete the contents of the directory given by:

FileNameJoin[{$UserBaseDirectory, "Paclets"}]

More specifically it appears to be sufficient to delete a single file:

FileNameJoin[{$UserBaseDirectory, "Paclets", "Configuration", "pacletSiteData_10.pmd2"}]

To prevent Mathematica freezing on the next start-up I need to turn off Automatically check for data updates in the Internet Connectivity tab of the Preferences menu.

I presume that some automatic data update is incompatible with my version; hopefully it will be identified and fixed.

I am posting this for anyone else who might have this problem and is in need of a quick solution.