Your regex is invalid. + is a quantifier that means "one or more of the prior thing"; having a quantifier directly on a quantifier doesn't make any sense in the regex mini-language. If you mean five word characters, say that: \w{5}.

Edit: Derp, yes ++ is now a valid extra greedy quantifier; point still stands that (using parens for illustrative grouping only) (++)+ doesn't make any sense which is why the error message points just after the third +.