Re: does anyone know, how to lock screen when on a call
 

I've been wondering that for a while...

Re: does anyone know, how to lock screen when on a call
 

sanmanc's suggestion where you use the stock phone keyguard works for me. Never had a problem when I had the disable touchscreen feature enabled.

Re: does anyone know, how to lock screen when on a call
 

For those that don't want to install any third party software:

The other way to lock the screen while in a call is to press the "option" then "end" buttons (together, option first). That will lock everything. You need to press the "ok" button to unlock after that.