Do you have members spamming your blog?

I am wondering if anyone that has had members spamming their blogs with ads for uggh boots or something like that, and have you had any issues with the .htaccess file or all links on main page after they registered? I have and every time i ban them things go wrong. Then I have issues with the .htaccess file so i delete them and then I had the wierdest thing happen, my .htaccess file was blank. I had to copy and paste info into it to get site back up. Now I have done no work on site, and this all happened after they joined, which by the way happened before also, but i reinstalled fresh and even my hosting account.

Yeah, I have had this same spammer on my PHPbb boards.  My boards were more experimental and not active, so I did not even notice until the number ran up to like 10k posts within a month.  Those boards are down and and I am working on getting new ones up.

Edited to remove the IP's & tips.  They server their purpose & this is what I promised I would do months ago.