I tried editing this question. It has "problem" in its title, so when I try to save it, I get a warning box telling me I should avoid using this word in a title. And I can't save my edit unless I change the title, which will make the edit non-atomic. I think only the OP should get this warning. Getting a box asking me to please change the title after my edit would be fine too.
The word "problem," among a few others like "question" have been blacklisted and you can't use them in question titles anymore. The question was probably created before this filter was in place (that's why the OP managed to post it), but now you can't edit anymore. You'll have to either remove it or work around it.
For what it's worth, I think this (the word filtering) is a terrible idea.
See related question: Why can't we use the word "problem" in titles?
Just give it a more descriptive title. See my edit for an example. (If there are any other edits you wanted to make, you should be able to now.)
The same warning does now appear when posting new questions.