Starting virutalbox causes ctrl, shift, alt and super key to stay pressed

[rubicus]

When starting VirtualBox, before launching any guest whatsoever, Windows starts behaving very peculiar. First, the VirtualBox window does not appear on top of other windows, but instead behind all open windows. Then the keyboard mostly stops working (I can't write anything anywhere, use alt+tab etc), and clicking anywhere there is text (for example a browser) starts marking text and I can't use my scroll wheel for scrolling through web pages. My left mouse button still works, but most right click menus disappear as quickly as they appear. If I try to launch anything (or switch to a running program) in the taskbar this causes a UAC window to appear. This behaviour continues after closing virtualbox, and the only way I've discovered to get rid of it is a complete reboot.

Thinking this seemed like ctrl+shift were pressed I proceeded to log some keys. Using autohotkey I managed to check what happens when I start Virtualbox, and it seems LAlt, LWin, RControl, RShift and F3 all get pressed down (but not up). This also seems to repeat 8 times (with a ~30ms delay in between each iteration).

This problem started happening sporadically for me about a month ago or so, when running my virtual machine (although quite rarely). I could not seem to identify any particular behaviour triggering this at the time. Today I upgraded to VirtualBox 5.0.16 and now the issue somehow turned permanent, and happens every time I launch, and it really renders the host pretty much unusable until next restart.

Although it is very clear that this change happened during my upgrade to 5.0.16, now it happens for more versions. I tried unistalling and reinstalling several times, with the problem remaining, and even tried 5.0.14 and 4.3.36, with the same issue happening on every startup of Virtualbox. I have made sure to turn off any program (including autohotkey) runnning in the background both during installation and running the program.

I run on a 64-bit version of Windows 10, using a swedish keyboard layout. The problem starts happening before any VM launch, but if it's of interest I only have one Ubuntu guest that I use for development sometimes. I can still launch my VM with this behaviour, but I can't seem to be able to use the keyboard in it. I'll attach a VBox.log of that running, in case it is of interest.

[rubicus]

I have also been able to find this post on stackexchange, from almost 2 years ago: ​http://superuser.com/questions/738374/virtualbox-causing-weird-behavior-in-windows-keyboard-issues-uac-popups

The description there exactly matches my problem, with the exception that I can't write anything at all, instead of only upper-case letters.

[rubicus]

I found out what is triggering this behaviour! I have an external numpad (my keyboard (a Filco Majestouch 2 tenkeyless) does not have one), that is connected through USB, and when this is connected, this happens. Removing this also allows me to get back to normal without restarting the computer.

I still thinks it's a very odd behaviour though.