Mac not reading my new 3G dongle???

[janabedford]

I have just bought a new SFR 3g Dongle and signed up for the pre-pay network. Account has been authorized and they said that even for the mac, I do not need to install a c.d for it to work. They said that I should just need to plug the dongle into the usb port and it will automatically run the installation programme. This works on other mac computers, but not mine. When I insert it, the finder opens with the SFR logo on it but then it closes in a second. Any idea as to why it is not reading it on my computer? Cheers