Question for Mac users

I'm having a strange problem on certain webpages that have text boxes... like on TPP where you review or respond to a review, and occasionally  also on gchat.  The problem is that the curser refuses to move forward and the text I input does a sort of "strike over" and doesn't move forward.  on TPP, it only happens when I hit "return".  If I write in one long paragraph, it's fine.  Otherwise, it acts stuck.  (I hope that description made some sense).  On gchat, I close the chat window and reopen it and it seems to reset.  I have NO clue why it does it on TPP.  I don't have the problem on other archives though I have a vague sense that it intermittently happens on other webpages that require text input.

Does anybody have a clue what might be going on and if so, how to fix it?  Thanks, guys :)  Any help or hints or even pointing in a potentially useful direction would be great.