There also seems to be another issue when using the 'Check IP against DNS Blackhole List' setting in the security settings area. When this is enabled you attempt to post new topics or posts you will have to submit them twice, the first time an error will occur stating it is invalid, then the second time it will submit it successfully.
While this is a topic for discussing RC8, all support requests should still be posted in the support forum. For all wondering, yes you should start a new topic for your issues. This topic is not meant for support.