The internet explorer version is "Internet Explorer 8.0.7600.16385".
I have done another test, from the same computer, and I can access to the web service, but the switch crashes when I try to login. From another computer connected to other vlan I don't have any problem to access de switch, and it has version "6.0.2900.5512.xpsp_sp3_gdr.100216-1514".
I think I should update the firmware, but I don't know if this problem has been fixed.