Virtualbox error (NS_ERROR_FACTORY_NOT_REGISTERED ) after Linux 4.20 and VBOX 6.0 update (Arch Linux)

After upgrading my Arch Linux system (Linux 4.20) and rebooting it, it fails to start VBox (now Vbox 6.0) Error message is: NS_ERROR_FACTORY_NOT_REGISTERED.

Vbox kernel modules are loaded (see below).

It seems everything ist fine, I don't know where to look for wrong config/install. If I do VBoxManage list -l I am getting same error messages below. /tmp folder is writeable for root and vboxuser

Any ideas?

vboxwebsrv -p 5678 -A null -H server.de
Oracle VM VirtualBox web service Version 6.0.0
(C) 2007-2018 Oracle Corporation
All rights reserved.
00:00:00.000097 main     VirtualBox web service 6.0.0 r127442 linux.amd64 (Dec 26 2018 21:56:59) release log
00:00:00.000100 main     Log opened 2019-01-02T20:17:34.687638000Z
00:00:00.000101 main     Build Type: release
00:00:00.000103 main     OS Product: Linux
00:00:00.000104 main     OS Release: 4.20.0-arch1-1-ARCH
00:00:00.000105 main     OS Version: #1 SMP PREEMPT Mon Dec 24 03:00:40 UTC 2018
00:00:00.000131 main     DMI Product Name: 
00:00:00.000141 main     DMI Product Version: 
00:00:00.000185 main     Host RAM: 15925MB (15.5GB) total, 10819MB (10.5GB) available
00:00:00.000189 main     Executable: /usr/lib/virtualbox/vboxwebsrv
00:00:00.000189 main     Process ID: 13728
00:00:00.000190 main     Package type: LINUX_64BITS_GENERIC (OSE)
00:00:00.021361 main     IPC socket path: /tmp/.vbox-root-ipc/ipcd
vboxwebsrv: error: failed to create the VirtualBoxClient object!
vboxwebsrv: error: Code NS_ERROR_FACTORY_NOT_REGISTERED (0x80040154) - Class not registered (extended info not available)
vboxwebsrv: error: Most likely, the VirtualBox COM server is not running or failed to start.
# lsmod | grep vbox                                                                                                                       
vboxnetflt             32768  0
vboxnetadp             28672  0
vboxpci                28672  0
vboxdrv               499712  3 vboxpci,vboxnetadp,vboxnetflt