Moodle in English

I have had students reporting that they have been having issues posting to forums. They will type in text and press the "post to forum" button but the message is lost and does not post to the forum. The attempt is repeated 2 or 3 times before the posting actually takes. This issue is not occuring every time they post to a forum but happens occasionally. I know that at least two of the students were using Internet Explorer could this be a web browser issue?