You are right ThinkInk - this is absolutely nothing to do with what Browser you are using. I have come across a similar problem. It seemed to be when I was trying to addd a linebreak in Contribute (SHIFT+ENTER). It gave me the same error message you are seeing. I am guessing the piece of text you were pasting in had a linebreak in it.
Sadly I have no fix for this yet - it is highly annoying. Will let you know if I come up with one.
It seems (looking around the web) that there are a number of reasons Contribute gives you this error. One of them being accidentally clicking outside the editable regions. This can happen if you have put the editable region inside a tag. For example:
<h2><!-- TemplateBeginEditable name="strapline" -->This is a strapline<!-- TemplateEndEditable --></h2>
In my case it was something completely different. I have used a PHP include file in the template for the website I wanted Contribute to edit. This was so the users could edit one file (a news panel) and see the changes reflected across the whole site. It seems this include file was confusing Contribute. It appeared fine in the editing window (though you couldn't edit it) but, for a reason known only to Contribute was causing the "You cannot perform this action in this region of the page" error every time anyone tried to paste text into Contribute or, bizarrely, add a linebreak.
I fixed it by referencing the include file differently... Originally I was using:
<?php include("newspanel.php"); ?>
so I changed it to:
<?php include("http://www.thewebsite.com/newspanel.php"); ?>
now Contribute lets you paste into editable regions and add linebreaks. Also it doesn't show the include file in the edit window meaning I am not going to get enquiries from clients who have been given an error message when they tried to edit it.
I'm not sure if this solution will help you fix the particular problem you are seeing but its up here now for others to read. Hope its helpful.
I had the same thing happen to me and found a fix to my problem which, of course, may or may not be related to your situation. Initially, I thought I had a "permissions" problem based on the error message but that was not the case. The problem was nothing more than a tiny bit of html code. I am not using templates on my pages but I am using several "includes" in each web page. I suspected one of the includes was the problem because if I stripped everything but the page content I could edit the page without getting an error. So, I began removing these "includes" one by one until I found the one with a code error. My offense was forgetting to wrap " " inside of <p></p> tags. I fixed that and the problem went away. There are probably hundreds of reasons why you are getting that message but a simple code error caused it for me. Good luck.
I have suddenly been confronted by the same problem - "You cannot perform this action in this region of the page."
Nothing fancy was happening. i just opened Contribute yesterday and tried to add a new PDF link in the middle of some text that had been there for ages so it was a "region" i had edited many times before with no problem and it was just a new version of a PDF that i had uploaded before. Because I have limuited permission i cannot do much with the code as suggested by RJD59 and am not sure what "includes" are.