The modem is detected without problems, apparently works fine but, when I do the call to my ISP (TelefonicaNet, Spain) the PPP program (KPPP and Gnome PPP) stays 20 seconds aprox. connected and then it dies. That's strange since my hardware controlled modem worked fine, and other versions of Ubuntu, installing by hand the LT modem driver worked right. The modem is a GM56LA manufactured by Genius and having an Agere Systems Winmodem chipset, that is in fact a standard LT winmodem chipset.
Steps to repeat:
Install Ubuntu/Kubuntu
Open KPPP or your dialing program
Set up the connection (in this case the ISP is Telefonicanet España)
Press dial up button
Wait and see the error code (16) and the register
Thanks for your support.
EDIT:I selected a wrong package, I meant the restricted modules for Ubuntu/Kubuntu 6.06, sorry for the mistake.
Note: the original reporter indicated the bug was in package 'linux-restricted-modules-2.6-38'; however, that package was not published in Ubuntu.
I've solved the problem following a howto from ubuntu forums "how to compile lucent modules" and it worked. It seems that the modules I've compiled have the 8.30 core version while the precompiled with the distro have the 8.31v. and it dosen't works!!! This may be a critical bug and it must be solved for the next distribution!!
thank you for your bug report :)