I'm looking into this right now. If you (or your customer) can provide any more information that would be helpful (product version, blacklist versions, blacklist names if there's more than one). Juniper is looking for the "product serial number", can the customer provide that as well?
What they've been telling me so far is that they don't provide blacklists (or web filtering with pre-defined URLs) and that the customer added the URL. So, we need more information.
Just an FYI: several years back WebSense (a filtering company) incorrectly categorized our website as a "hacking" website, and any routers/switches/servers that used that WebSense filter were incorrectly blocked from accessing wyday.com. We reported that immediately and got that fixed, however if your customer is using that old filtering blacklist then that might be the problem.