WebToLeadForm javascript error

Every time a page with a WebToLead form is opened in Chrome I get the following error in the Console:

VM9238 sugar_grp1.js?s=69ebae0…&c=1:147 Uncaught TypeError: Cannot read property ‘lang’ of undefined

I tried commenting out the following portion of code at line 147: trim=YAHOO.lang.trim;

At this point the error changes to:
VM9238 sugar_grp1.js?s=69ebae0…&c=1:966Uncaught TypeError: Cannot read property ‘lang’ of undefined

(anonymous function) @ VM9238 sugar_grp1.js?s=69ebae0…&c=1:966
(anonymous function) @ VM9238 sugar_grp1.js?s=69ebae0…&c=1:986