iTunes 12.2.1.16 only crashing -- unless wifi is turned off

Using MacBook Pro with OS X 10.7.5.

Just updated iTunes to 12.2.1.16, and since then iTunes will only work with wi-fi switched off. Otherwise it freezes within a few seconds.

Which means no iTunes Store, no downloads, nothing that requires wi-fi to be on at the same time as iTunes.

I don't really want to go back to an old version of iTunes. The new version has improved operating speed. But there must be a bug in 12.2.1.16. Has anyone discovered exactly what it is and whether it's fixable?