There have been a few occasions recently where people are replying to the forum notification telling them they have received a PM. What that does is send an email to the admin email account, it does not send a message back to the originator of the PM.
So, when you receive a notification (by email) that you have a PM, read the message, it will say 'to reply to this message click this link' (or something similar).
Alternatively, log into the site and reply to PMs that way
