The forum regularly fights off spammers, and has a variety of filters used for this. Occasionally the filters "catch" something they don't need to. I also have gone through spells when I've been unable to post, especially when I'm including a link, but sometimes when there is no link. Sometimes too few words can trigger it.
Some folks have discovered that it works better when they post without the link, then edit their post to include the link. Other times things just work as they are expected to.