It's on Invision's end. Most likely server overload. The database can only handle so many queries per second and the limit has probably been reached. It happens quite frequently on large popular forums with 100k+ members. We're not that large, but there are thousands - maybe even tens of thousands of different forums on the z7 server.
PM System temporarily offline. Please check back soon.
When I send a PM, it says the PM has been succesfully sent, but then when I look in to the "Sent Items" folder there's nothing there. I tried refreshing the page and still nothing. Why is this happening?
Well, I can send messages fine once again, anyway, even though I can't see what I sent in the "sent messages" section