IE7 textbox onfocus

Because IE won't do document.getElementById(ID).setAttribute('type','password开发者_运维技巧') I've re-engineered the way the password field works on this site so it works in accordance with this idea.

It works fine in IE8 and FF3. It breaks in IE7 just as you click into the password field. I'm now tearing my hair out. Can anyone give me a clue what's wrong as IE7's diagnosis is just "Object expected, code 0"?

You can enable script debugging in IE7 to get a more meaningfull error message, however you get the same error in Firefox and probably other browsers, Firebug in firefox is giving me the following error.

You have the error 'passwordChange1 is not defined'