So, besides what I wrote in mint forum this what I noticed:
- if I choose session type to KDE plasma.... failsafe mode - all works ok - I can change pulpits, add panels, all submenus are visible, I can see multiple windows.
- if I choose other session type f.e: KDE plasma, Default - I cannot see submenus and pop windows, only one window is visible, other dissappears, but using alt-tab I can switch between them
- I tried to clear cache (as I found somewhere in forums) in /var/tmp/kdecache-myuser and deleted all plasma* files but it didn't help
- I did deleting also from new user account i created but it didn't help 
- new user account was set perfectly, I found no bad behave

If any one could just told how to restore default KDE/plasma looks.

I did updates and upgrades and dist-upgrades like in this thread:
http://forums.linuxmint.com/viewtopic.php?f=109&t=124912#p684113

Reproducible: Always

Steps to Reproduce:
1.login using KDE plasma desktop or default session on my account
2. all works perfectly when I use KDE plasma failsafe mode
3.all works perfectly for new user created after updating to 4.10.3
Actual Results:  
I'm using KDE-failsafe mode to login

Expected Results:  
I can log using default or KDE plasma sessions (no failsafe mode)