Could be a number of issues.
Try clearing the cache of your browser. Only clear the AZ parts or you'll find yourself logged out of all your favourite sites. Also try another browser.
It could be your antivirus program has decided this forum is malicious. Equally an anti malware program may be doing the same. Try disabling your AV and / or AM program and connecting to AZ. If that doesn't work then it could be your internet service provider has decided AZ is way above your paygrade either on their own volition or by government order. Getting around that may require you to use an open DNS service (I assume here you are using an ISP provided router). This means logging in to the router settings and changing the DNS to something such as Google's. Many ISP provided routers will not let you change that though. Also you may have parental type services by default with your ISP. They may have mistakenly listed AZ. Check out yor ISPs parental nannying settings. Many of them default to on. Also try a VPN or proxy service to connect to AZ. You can find a feee one to try to connect. Free ones are usually poor but it will prove the concept or not.
If none of that lot works post a screenshot of the message you get and it may narrow the focus.
Strange as I had much the same prob a couple of weeks ago. Couldn't open AZ site at all though other sites seemed ok. Can't remember the exact error but it did mention a site virus infection. AVG found nothing wrong and neither did Malwarebites. Searching for a cure also suggested cache clearing and various things which were not applicable to Firefox.
I'm running an elderly Win7 PC with Sky and using Firefox and Thunderbird and have been having lots of probs recently. Had been unable to reply to emails at all for a week or so until I swapped over to Yahoo mail which allows me to keep my sky email ID and that's working fine. The blocking of AZ site happened some time later and was a problem I couldn't sort so eventually restored the PC from a full backup disk and all is OK now.
If turned off virus protection and it works, but I don't want to leave it off, so I added atomic zombie to the exceptions, and that helps, but I still can't get to the forums section. Avast says that it will make an exception for the entire domain, but it doesn't seem to be working.
You may find that the problem has gone.
I reported the problem to Avast.
They have just sent an apology.
Thank you for reporting this false positive.
We have now cleared its reputation in our database based on the findings and removed the detection. This change may take up to 24 hours to take full effect. Please accept our apology for the inconvenience caused.
If the detection persists after 24 hours, update the virus database in Avast anti-virus and reply to this email with the attached files:
1.Take a screenshot of the Avast detection dialog (Threat Secured pop-up with See details - displayed at the bottom).
2.Take a screenshot of the Avast virus database (open Avast antivirus and go to Menu > About).
We hope you have a nice day and stay safe online.
Avast Malware Analysis Team
Enterprise Office Center, Pikrtova 1737/1a, 140 00, Prague 4, Czech Republic
Last night I shut down my PC which I don't usually do (I normally just set it to sleep so I don't lose all the sites I'm logged on to). Started up today and found I could log in to AZ but when I tried going to 'forum' I got that same 'URL. Blacklist' from AVG and PC refused to open the forum page although all other sections of the site worked fine?
Spent a while looking for a cure but all suggestions seem to be for the web owner for sorting out a web site that has been Blacklisted on some database somewhere.
Decided to leave it for a while but later I opened some emails and one was a notification of new AZ forum posts. I clicked the link in the email and forum has opened now and working fine.
I mailed Brad with the exact error message just in case there is a glitch his end but suspect it's a PC rather than a website problem. I'll leave AZ open til I have to shut the PC down again and see what happens then. Maybe try playing about with AVG or swapping over to Avast if still having probs.