[jQuery] $(this).text().trim().toLowerCase() throwing errors in IE

[Magnificent]

Hi all,

I'm running into an IE7 problem where the Visual Studio debugger is
saying:

"Microsoft JScript runtime error: Object doesn't support this property
or method"

Visual Studio is highlighting this line as the problem:
 if($(this).text().trim().toLowerCase() === subToBold

$(this) should be the li.
text() should be the text/content of the li.
I then trim/lowercase it.

The pertinent code block is below, the "lis" are list items I'm
iterating over, I'm checking if the text of the li is equal to a
dynamically populated hidden form field on the page.  Code all works
fine in Firefox, but throws errors in IE, any ideas why?

if(url[7] === 'default.aspx'){
     //if we're on default.aspx we don't want to bold the hidden form
field subnav so do nothing here
} else {
     //bold the hidden form field subnav
     lis.each(function() { //iterate over each subnav to bold
          if($(this).text().trim().toLowerCase() === subToBold) { //
text of each subnav, trimmed to strip whitespace
               $(this).css('font-weight', 'bold');
          }
     });
}