[Lilux-help] Problem with a Huawei USB modem and Linux on a Asus laptop

Hi, I've been experiencing a very bizarre problem : I have an ASUS laptop with Windows Vista and a Huawei USB modem with a Tango subscription [mobile internet]. It works just fine under Vista. A couple of days ago I got from a magazine a DVD with several Linux distributions, I tried some of them [namely Suse and Mandriva] in the live-CD mode [running from the DVD] and they seemed to work fine. They even recognized the Huawei, configured it without a problem and the internet connection was pretty good. As a matter of fact much faster than Windows ! So, I decided to install Mandriva on the hard disk, installation went just fine [multiple boot with grub], and internet was excellent. And then I shut down and when I turned the PC on the following day, I had no internet and Mandriva did not even see my Huawei modem! I tried several times with the other distributions from my DVD but nothing. Huawei had disappeared completely!!! Still I can use it without any problem from Windows ! Does anybody have an idea ? Who can help me ? thanks in advance Nikolas NASSOS