I got an email saying 'you have been sent a PM by xxx entitled xxx' but when I clicked on the link, it came up with an error message saying 'this message does not exist'. It also didn't come up in my inbox. I've archived all messages so the folders are empty, but nothing has happened. Can anyone help?

Did the sender delete the message? I've never tried, but I think you can delete messages from the message tracker if they haven't been read yet.

Thanks, that's probably what happened. Don't know why though!

Yep, you can and the email will remain.
PM the person who sent it to ask

I might. But then, if they deleted it, it probably isn't that important to tell me whatever it was At least, they haven't sent me another one.