The firmware of the XBee S2 modules starts with 82xxxxxxx, refer this link, http://www.digi.com/support/productdetail?pid=3430&type=firmware
Are you using latest X-CTU?
Here is the link for latest X-CTU software, http://ftp1.digi.com/support/utilities/40003002_C.exe
Still if you are having problems with the WEB, download the required Zip file from the Digi website and got o modem configuration tab in X-CTU, click "Download New Versions" and select File as the option, browse to the file.
For the problems in downloading new versions from web, you need to contact digi technical folks, create an onlone support request at the following link, http://www.digi.com/login?ReturnUrl=%2fsupport%2feservice%2f