The Forum was recently subjected to a massive spam attack. I estimate around 800 new spam topics were created along with created along with thousands of comments.
The comments and topics have now been deleted, but to prevent further attacks I have had to suspend new account creation for the time being and have deleted a number of new accounts.
I hope that no genuine comrades have been caught up in the crossfire but I can't guarantee that this is not the case as the interface in question is a bit of a blunt instrument.
As I write, new topics are still being added so the disruption may still be with us for a while.