None of the browsers that you state are having problems are supported for EPiServer CMS 5 R2. (Only IE 6-6 + limited support for Firefox 3, see release notes for more details:
It's possible that we will release patches/hotfixes for IE9 and Firefox 4 but it's not something that is currently planned.
EPiServer CMS 6 R2 will have support for IE7-IE9 + Firefox 3.6-4.
EPiServer Development Team
Im using Episerver 8 and I am also getting this error
I've created new form in XForm editor. Its name is "TestForm". It's very simple. It consists of single textbox "Name" with obligatory value and submit button that simply save textbox value to database. Form can be send without logging. "" option checkbox is checked. Form folder is set to "No folder" value. "Page shown after the form has been sent" is specified.
While trying to save this form (using Internet Explorer 9 or Safari 5) the message is displayed on top of the XForm editor window "Incorrect form".
Trying to do the same with Chrome 10 the tooltip-like message appears near the textbox "Please fill in this field" + textbox's tooltip and a stays unsaved.
Firefox 4 behaves correctly closing XForm editor window and saving newly created form.
Described behavior is for EPiServer CMS 5.2.375.7.
Am I doing something wrong ? (maybe it's just a bug)