Are you a VPN or Ultrasurf user? If you are having problem connecting to VPN or Usurf on your mobile broadband modem, one of the reasons is a wrongfully configured APN or Access Point Name on your dashboard.
You might not know is that whether TCP or UDP you want to use, it depends on what APN you are using.
And for my own observation, UDP is more stable than TCP connection if you are using VPN or proxies on mobile broadband, although similar in speed.
For VPN you have the option to choose from TCP or UDP connection, it is within your VPN config. While for Ultrasurf, only TCP connection type is allowed.
SMART TCP APN: smart1, mms, smartbro
SMART UDP APN: internet or any working access point aside from the SMART TCP APN given above.
GLOBE TCP APN: www.globe.com.ph
GLOBE UDP APN: http.globe.com.ph or again any working APN aside from GLOBE TCP APN and it will still give you UDP.