I have noticed with the upgrade that the modem does not search for a signal automatically...only when you run the dialer or MySignal, will it actually start searching.
The other option may be that the modem is not connected properly to the PC, may explain why MySignal doesn't work!!! If it is connected (Check in Device Manager), re-install the Sentech software. If that doesn't work, go to a friends house with a PC, re-install from scratch (pref a friend who lives near a tower).
Good luck.
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...and Gandalf stared into the distance with a faraway look of gold...