I am having a E65, i am trying to connect to wlan in my office and i am unable to browse internet or use the mail for exchange.

It is connecting to wlan ( it is asking a preshared key and i provide the same), all the other setting like DNS, ip all provided in my office internet is connected through a proxy server which requires user name and password.
i have provide the proxy also

wlan mode is infrastructure
security mode is wpa/wpa2
security setting i provide preshared key

when i am connecting it does connect to network, but unable to browse internet. it is showing unable to perform operation and cannot connect login credentials not found

i didnt find a place to provide user name and password

can any one assist me on this