I have recently installed Ubuntu 12.10(64 bit).
But was not able connect to internet using my MTS modem.
It detects My modem, but says 'not enabled' even after enabling mobile broadband.
But some times, very rarely (once in a day) the 'not enabled' changed to somthing like 'CDMA home network...evdo' and then i was able to connect.

I googled around and found that this is due to buggy 'modem manager 0.6.0.0' which comes shipped with ubuntu 12.10. So I removed it using software center and installed modem manager version 0.5.2.0) from a .deb package i have downloaded, using this code in terminal.

sudo dpkg -i modemmanager_0.5.2.0-0ubuntu2_amd64.deb

The problem has gone even worse. The bad part remained bad while the good part worsened.
Now i can't connect to internet even when the 'CDMA home network...evdo' appears in place of 'not enabled'.

People found the solution working, every where around different forums.
What could have gone wrong with mine??

I have posted the same on ubuntuforums.org but no reply yet.

Update

Now ubuntu is giving an error message in notification area. So far what i have understood is, it is due to the modemmanager_0.5.2.0 i have installed. It requires some sort of umnet dependencies. Since i have installed it offline through .deb package i think it lacked some dependencies. But since i can no more connect to internet i cannot repair the dependencies. Kindly reply if you have any idea about umnet dependencies or something related to it.