The best way to report a bug is to first search the RichFaces User Forum to see if it has been discussed or resolved before. You can also search RichFaces JIRA Project because it might already have been found or fixed.
If it has not been discussed before I would recommend creating a new forum post describing the issue to get some feedback. If you are really sure that this is an issue with RichFaces then go ahead and enter new RF JIRA. Be sure to provide enough information so that the developers can reproduce the issue and understand your setup.