unlocked huawei E3131 accepts some sim cards and some don't work? Error 619?

[malend]

there are 4 mobile operators in my country and i unlocked my modem recently such that it could work with all of them. the problem now is after unlocking 3 off the operator's sim cards work properly (including the original card) yet one of them doesn't work.

When i tried to connect i get error 61; it dials, checks username & password, registering computer on the network>>then instead of Authenticated i get "unable to connect error 619: Connection to the remote computer could not be established, so the port used for this connection was closed."

What i have already tried to do;
I have checked the internet profile settings are are all intact including the apn
i have uninstalled and re-installed the modem
i have updated the modem drivers

[Valdemaras]

Please check in device manager if no other devices uses ports that your modem is detected/used by. The try to set connection settings manually to a specific one GPRS/GSM only OR 3G/WCDMA/HSDPA only as your network connection type preference, then check connection again.