Guten tag Alexander,
I have not updated any of the information since updating to Feisty and have also not used Smartlink for a long time. The Conexant open drivers that you have tried, do not work on the Feisty of Edgy kernel version and fix has not yet been found. The thread has some posts in it if you read them. The only way at the moment is to download and install the free Linuxant driver for your HSF modem at: http://www.linuxant.com/drivers/hsf/full/archive/hsfmodem-7.60.00.09full/hsfmodem-7.60.00.09full.tar.gz
These drivers are free, but restricted to 14.4k and can be opened up with a registration code that you get on paying a fee, but at least will allow you to test and get online. they also have a deb file, but i am not sure if it is for the latest Feisty version or not.