Lenovo ThinkPad Edge E520 (Core i5) with Conexant 20671 SmartAudio HD. 

PROBLEM DESCRIPTION: Same problem as described in the post below.  Skype interrupts a call after a several seconds reporting "Skype can't detect sound card" error.  After experimenting with sound card settings  the problems seems go away but return back after the first program restart.  In short, update to the newer sound card driver version fixed the problem. The post below helped very much. I sincerely thank gentlemen who took time to communicate the problem and solution to community:  T420 sound card problem causing Skype crash

SOLUTION:

Here is how I resolved the aforementioned problem on my E520 which I have ordered directly from Lenovo in May 2011. 

Download and install the most recent driver from Lenovo site here:

Conexant Audio Software for Windows 7 (32-bit, 64-bit), XP (32-bit, 64-bit) - ThinkPad Edge E420, Edge E520 

This is what I had "before" and "after" on my system. This is the old driver "before":

This is the newly updated driver "after" the update:

For the record this is my system settings:

Moderator note; added picture warning to subject for picture(s) totalling >50K Forum Rules

THANK YOU!!!!!!!!!! I have been messing with this for WEEKS!

THANK YOU THANK YOU THANK YOU!!!!!  I have wasted so much time trying to get this sorted.  You solved it and saved me from ripping my hair out!

The Thinkpad System Upgrade does not cover driver version upgrade. Needles,  to metion the Windows OS Automatic Upgrad too.  All drivers upgrades come in software pachages and you can install it only manually downloading them.

Here is the driver downloads and upgrade packages page:  

Drivers and software - ThinkPad Edge E220s, Edge E420 and Edge E520