unable to login tvbnow.com using firefox

i try to use firefox 3.0 to login in tvbnow.com. after login and try to redirect to the original page, my status becomes guest.
i use to memory function to store the login id and password, but it is no avail
i know that i can use ie to browse tvbnow.com, but i prefer to use firefox as my friend said that my computer may infect easily with trojan if using ie
thanks