HTTP Error 403

In the last few hours one of my blogs (on ver 2.2) has received a 403 error thar is displayed for the incoming links section and the “Other WP News” section of the dashboard.

Within the last few hours I attempted to publish for the first time since the error appeared and received the same error. The error reads as follows:

Your Internet Protocol address is listed on a blacklist of addresses involved in malicious or illegal activity. See the listing below for more details on specific blacklists and removal procedures.

Your technical support key is: 7c68-ca14-1366-73cd

You can use this key to fix this problem yourself.
The link as quoted above is also part of the error page.

In addition, I have three other blogs on this same domain one runs ver 2.3.1 a second runs on 2.3.1-RC1 and a third runs on ver 2.2.

None of these three have experienced the same error and are operating fine and on the same server.

The server is not mine but provided via a hosting service.
My T/S efforts have included performing two virus scans and two scans for spyware with no positive results.

Obviously the problem is not WP ver specific or related to the server all four blogs are located on as it only occurs on the single blog.

Has anyone had this problem before and found a solution to it?