Nope, leave it as it is then .. curious .. I really am at a loss as to why it works for some people and not for others. Try turning off everything except the nUI stuff and see what happens then. At least that way we have more control over what to change if anything between me and Scott if it still happens
If it works then that must mean *sherlock holmes impression incoming* that it undoubtedly must be one of the ones you just turned off. So turn them back on one at a time and try again. Once you find which addon looks to be the cause, see if there is an option on it somewhere to do with the chat frames.