JavaScript error occur when posting a new message

I get the following JavaScript/JScript error when posting a new message:

Object Required
var prevIdx = document.getElementById("_ctl0_MainContent__ctl0_PostForm_PostAttribute_0").tabIndex;

It occurs as soon as the AddPost.aspx page is loaded.

[272 byte] By [DavidM.Kean] at [2008-2-6]
# 1

What browser are you using? I can't repro with the latest IE and standard settings.

JoshLedgard at 2007-8-21 > top of Msdn Tech,Feedback for forums and MSDN websites,Bug Reports for Forums website...
# 2
Josh, I am using IE with Windows XP SP2.

It's strange, it has only just started happening in the last couple of days.

I'm also getting an similar error when I enter text into the search box that at the top of a thread:

Object Required
return clickButton(event,'_ctl0_MainContent_PostFlatView__ctl0_SearchRedirect__ctl0_SearchButton')

DavidM.Kean at 2007-8-21 > top of Msdn Tech,Feedback for forums and MSDN websites,Bug Reports for Forums website...