Hi Marc,
A couple of months ago the PM facility was changed to only be allowed after a member had 10 posts. Unfortunately, we got a lot of people jumping on the site, posting once to advertise their site, then sending out PMs, so we had to put in the limit. For the most part it seems to have worked pretty well, but apologies if it's caused you any inconvenience.
The good news is that after only one more post and you'll have it back again
Stu