I have a 536ep which I have managed to get working. I am still using LM9.0 but my solution may be of some help to you.
After booting up if I try to start kppp the machine locks up and the keyboard ceases to function and I have to power off and reboot.
However if, before starting kppp, I launch minicom, wait for about 20 - 30 seconds until an AT line appears on the terminal screen and then close minicom I can then start kppp and the modem works perfectly until I have to reboot and then I have to go through the same process again.
I've no idea what minicom does but it solves the problem for me.
HTH
petew