I've had this problem for awhile now that has made the Plasma environment unusable for me.

Whenever I log into Plasma and try to launch an application from the start menu, Plasma (and the whole desktop, except for the mouse) completely hang, and never un-hang.

From the tty, looking at process monitor shows plasmashell using up 100% CPU of a thread.

Here is the stack trace from the process, as retrieved by dgb (looks like I am missing some debug symbols but not sure which package I need to install):
:~$ cat gdb_plasmashell.txt 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
0x00007ff7110c84d4 in ?? () from /usr/lib/x86_64-linux-gnu/libGL.so.1
#0  0x00007ff7110c84d4 in ?? () from /usr/lib/x86_64-linux-gnu/libGL.so.1
#1  0x00007ff70d0e1be8 in ?? () from /usr/lib/x86_64-linux-gnu/libnvidia-glcore.so.358.16
#2  0x00007ff70d0a36a3 in ?? () from /usr/lib/x86_64-linux-gnu/libnvidia-glcore.so.358.16
#3  0x00007ff70d0c3d78 in ?? () from /usr/lib/x86_64-linux-gnu/libnvidia-glcore.so.358.16
#4  0x00007ff70d0c41e0 in ?? () from /usr/lib/x86_64-linux-gnu/libnvidia-glcore.so.358.16
#5  0x00007ff7110b8403 in ?? () from /usr/lib/x86_64-linux-gnu/libGL.so.1
#6  0x00007ff707c96122 in QGLXContext::swapBuffers (this=0x346f980, surface=0x2770ba0) at qglxintegration.cpp:529
#7  0x00007ff715af5e26 in QOpenGLContext::swapBuffers (this=0x347f410, surface=<optimized out>) at kernel/qopenglcontext.cpp:992
#8  0x00007ff7187cdec9 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#9  0x00007ff7187d329c in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#10 0x00007ff7155c02be in QThreadPrivate::start (arg=0x3471a00) at thread/qthread_unix.cpp:337
#11 0x00007ff7146af6aa in start_thread (arg=0x7ff62f0e1700) at pthread_create.c:333
#12 0x00007ff714ed8eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Here's some background info:
Ubuntu Unity environment works ok, using sddm (Plasma fails using sddm)
Using latest NVidia 358.16 Unix driver from the official NVidia site.

:~$ uname -r
4.4.0-040400-generic

:~$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=15.10
DISTRIB_CODENAME=wily
DISTRIB_DESCRIPTION="Ubuntu 15.10"

I've tried deleting the .kde, .cache and .config folders as well and that also did not fix the problem.

Is there any other info you need from me, or do you guys have any idea why I am experiencing this problem?

Reproducible: Always

Steps to Reproduce:
1. Log in to Plasma
2. Start an Application from the Start Menu (any application)
3. I am hung

Actual Results:  
plasmashell consuming lots of CPU, everything on the desktop except for the mouse cursor is frozen. Does not unfreeze.

Expected Results:  
Started the application.