Unfortunately, it's largely due to one of two things -- an IP block that your internet service provider is using that has a lot of suspicious activity coming from it or (b) activity from your IP itself that is suspicious or has weird display characters in it (an occasional post on our site might even trigger it). It's an automated security and traffic filter, so there's nothing we can do to "fix" the issue, and it usually resolves itself within a day or two.

If you find it happening only with a specific thread or PM or something like that, send me a PM with the details and I'll be happy to look into it further....

Sorry.