When you are the first time using HSDPA/HSPA modem on Ubuntu 9.10, you will not encounter any problem. However, when you use the modem the second time, it hardly to get the DNS. As a result, you cannot surf the internet.
Therefore, you should write the DNS down when you insert the HSDPA/HSPA modem to the Ubuntu 9.10 the first time. Add the DNS to the Network Manager by editing "IPV4 Setting" - "PPP address only".
The following are some service providers in Hong Kong :
3HK -
Primary DNS 202.45.84.67
Secondary DNS 202.45.84.68
CSL, One2Free, 1010 -
Primary DNS 192.168.63.101
Secondary DNS 192.168.63.102
Smartone Vodefone - unknown to me
That's all. See you!