I've been reporting my suffering over the last months over at ut99.org:
ACE Timeouts caused by my ISP?
I must admit I skipped posting about it here before as I hoped to receive good feedback there (what I did indeed), but yeah, in the end it must be Anthrax to see my troubles in order for something to change. So, consider this thread here as a desperate reach out to Anth.
To cut the long story short: ACE is no longer compatible with at least one ISP out there. I'm speaking of Unitymedia, a german coax internet and cable television provider. Every user will be kicked by ACE after 7 minutes for timeouts during the checks. Period. It's nothing related to the client side environment, it's something the ISP is doing which will cause ACE to kick for timeouts. The only way I was able to avoid the behaviour was using a VPN. Now, this is a point where I it gets kinda urgent to get something going; as this 'bug' is blocking players generally out where they can do nothing about it at all. Demanding updates for better security / features can reasonable be delayed; but having a malfunction preventing regular players from playing with no mistake from their side is neutralizing the advantages of any AntiCheat.
So yeah, if you read this anth, I deeply plead you to read my thread at ut99.org and consider doing at least a small update handling this bug.