I've just spotted http://jira.jboss.com/jira/browse/RF-176 reporting the same thing. Sorry for the duplicate.
Unfortunately it was closed with 'no fix', stating this is an IE6 bug that works better in IE7. All my users are on IE6 though so I guess I need to find another component. Can anyone suggest an alternative please that's compatible with Richfaces - I'm impressed with RF and using several other of its components.
The Tomahawk inputsuggestajax works for a while then freezes IE after about ten page refreshes. I haven't tried the Blueprints software but I've read that it doesn't mix very well with other libraries. I haven't managed to get Icefaces to run with RF yet.