I can't seem to find any talk/reference on this exact error, but in the jQuery core file at line 1298 (inside the "attr" function)
the line ==================================== elem[ name ] = value; ==================================== was throwing an error in IE7, preventing some other script-related things from working Using both Visual Studio 2008 (to debug IE) and Firebug (to follow along what was happening in FF) turns out "NaN" and "NaNpx" were respectively being passed into this function from two plugins i am using ("ui.datepicker" and "clickmenu") Saw that value come through in FF, and the browser just ignored it.... but when that value came down in IE7, its much worse as it throws a script error.... in the case of trying to "close" the Datepicker, this error prevented that close action from taking place, in the case of the menu, it was able to get by it and still work (but still presented the yellow alert in the bottom left of IE) Anyways, i added a few lines to the core, so that it is now like: ==================================== var FixedValue = "" + value; if (FixedValue.length >= 3 && FixedValue.substr(0,3) == "NaN") { value = ""; } if ( value != undefined ) elem[ name ] = value; return elem[ name ]; ==================================== And now my menu works without throwing the error and, more importantly, the DatePicker closes properly.... I guess my questions to the group are: 1) Has anyone seen this error from either of these plugins in IE7? 2) Think my 'fix' is low impact enough that I shouldn't worry about other things getting affected? btw, even this super stripped down page displays the error here on IE7 ==================================== <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Date Pick</title> <script src="../ScriptLibrary/jQuery/1.2.3/jquery.js" type="text/ javascript"></script> <link href="../ScriptLibrary/jQuery/plugins/ui.datepicker.css" rel="stylesheet" type="text/css" /> <script src="../ScriptLibrary/jQuery/plugins/ui.datepicker.js" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function() { $(".Date").datepicker(); }); </script> </head> <body> <div><input type="text" class="Date" /></div> </body> </html> ====================================