You should upgrade to Ubuntu 9.10. All the popular Mobile Broadband companies such as Virgin are pre-configured in the newest version of Ubuntu.

In fact, I was able to tether my cellphone using Ubuntu as a mobile broadband device without requiring any extra work other than changing the DNS setting to [url]opendns.com[/url].

Virgin Mobile is a global company so we're not exactly sure about whether you need to fine-tune any settings. There's some info about Virgin Mobile dongles in ubuntu,[url]http://ubuntuforums.org/showthread.php?p=8630531
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in OpenSuse:
[url]http://forums.opensuse.org/hardware/429207-huawei-e169-setup-help-needed.html[/url]