Usually when this happens it's because there is a strange symbol in what you are trying to post. So if you are for example copying a text from a word document and in that copied text there is a strange symbol then you'll be refused to post.
As you can post here and reply in this thread it seems to be working fine, and the problem is only related to that thing you want to post in the quick questions. right?
Actually, the problem seems to be how much I post. A short, one paragraph post such as this poses no problem.
My "Quick Questions" reply was several paragraphs long, written entirely in the forums post editor. The second time I tried, I copy and pasted it into notepad before I submitted it, and have been using that copy ever since.
The only symbols I've been using are:
: , . ? ! ( )