Apache hanging when making configuration changes

I’m running FreePBX 2.10. All modules are up to date.

At some time in the past, I started to get a problem whereby I’d make some changes to the config OK, but when I clicked to Apply the Config, apache never returned. Killing httpd with a HUP signal revealed that the changes had been applied and I could continue.

Whilst this was only happening when I applied the config, I was too lazy to try and fix it. However, it is now happening on nearly all config changes as well.

I can’t see anything in the messages, access or error logs to reveal a problem.

Any ideas?