Totally unprofessional and a complete joke. Will never use them on a production system again. Always angry if they are mentioned here like they are a legitimate choice...
Your case sounds like one of your IPs got blocked in their firewall, which can happen if you use bittorrent or receive a DMCA strike. But then other IPs associated with the domain would still work fine.
That said, yes, their abuse team is rather trigger happy. I've had disagreements with them, too. They can be VERY German ;) But in general, calling them on the phone can fix these cases within minutes.