Civi 4.4.6 forms not working with WordPress 4.3.1
Turns out it was the Jetpack plugin causing the problem and not the WP upgrade. I had installed Jetpack just after upgrading in an attempt to solve a different problem (unrelated to Civi). I should have tried disabling plugins before doing the downgrade, but previously no plugins were causing problems and I'd forgotten about the addition of Jetpack.