This happens because El Captain is only compatible with the libraries from VirtualBox 5.0.8 or later. VB Versions below 5.0.8 won't run on El Captain and you'll need to upgrade.
Actually not true. I have been running VirtualBox from the pre-release version of VB 5.0 up to 5.0.8 on OSX 10.11 since the first developer seed through 10.11.1 beta 4.
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I have the still the same Problem with 5.0.8.
The onliest version which is running under OS X 10.11.1 is VirtualBox 4.3.28. My Problem with this version is that no USB devices are able to be blinded.
Do anyone have a idea what could help.
Nows anybody how to install the missing Kernel driver on OS X 10.11.1?
The solution for this issue is uninstall the VirtualBox using the Uninstall Tool which comes included on the installation package and then install the newest version for OS X El Capitan, in my case VirtualBox Version 5.0.32 r112930.
Thanks Salim for letting us know.
Funny thing that today ticket #16474 was opened (and closed immediately) for the kernel drivers and their installation, that offered another solution that might help others as well. The solution was as simple as yours; reboot the host.
BTW, the latest versions are the 5.1.x series, at 5.1.14 as of this writing.
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