[Milhouse]

What's going on when I boot and it says "A start job is running to create volatiles files and directories" (I might not have got that exactly right as it's scrolled off the screen now)?

Last time I went to use my Pi it was frozen and non-responsive, so I rebooted it using the cmdline on my PC (to avoid corrupting the SD by doing a hard reset) but I got this message and it wouldn't boot.

I've just overwritten the files on the PC-accessible partition with those from #504 but I'm still getting this message. When I've had this problem in the past I've had to start from scratch and write a new image to the SD to clear the linux partition.

It seems to have done a bit more than it has in the past as it's thrown up a load of messages, the last of which is "Starting Avahi defaults" but that's been there for several minutes now so I don't think it's going to boot, so will I just have to wipe the card again?

Not really sure, that's the log message from a systemd unit that you wouldn't normally see unless the unit has failed or a prior unit has failed. Can you provide a link to [inline]journalctl -a | pastebinit[/url]. It could be you have some corrupt files or a corrupted file system in the second partition - if you are able to run fsck.ext4 on the second partition it should tell you if the file system is clean or not, and hopefully also fix any issues.