Hi all, there appears to be a forum bug whereby when you're trying to send someone a PM it auto-populates the To: field with "<HTML>" (including the quotes).
I'm not sure of the root cause of this yet, whether something has changed on the forum or whether a Windows update may have caused this.
Update: I have tested from a non-Windows environment and the issue is the same.
In the meantime, there is a work-around. Click on "Find Members" to the right of the To: field, and input forum members aliases there. You can then send the PM as normal.
I'll update as I progress towards a proper fix.