I am not aware of such a problem in Firefox and EnableResize
works fine on my end in Firefox.
You can see my test with the latest version 2011.1.519 in http://screencast.com/t/yOlbqd34w
My suggestion is to make sure that you are running the latest build of Telerik.Web.UI.dll as well as test in Firefox 5.
Another way to hide the resize handler is via the following CSS class:
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