I think, from the little, and rather useless amount of code, that you might be trying to access the cookie before you have created it.
I'm not 100% cos you haven't posted the code. If line 448 is var cookieName = this.GetCookieName() then that might be the reason. If you could post the whole code, I prolly will be able to get it from that
var cookieName = this.GetCookieName()
var cookieStr = this.GetContentsSerial(this.cookieColDel, this.cookieRowDel)
var cookieExp = GetCookieExp(this.cookieLifetime)
As jerry said, most peple here use VBScript (tho JScript is said to be more powerful). I'll see if I can get a little time and to some reasearch