When I PM, it blocks me from browsing the forums for a while and I can browse the forums again after...
But first my PM changes into this:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, firstname.lastname@example.org
and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
It did not sent, it just generated this.
That's not cool if you get as much PM's as me :S