I am sorry to hear that. However, I just tried to reproduce your scenario and doing uninstall and then clean install of both VirtualBox and Avast resolves the issue.
SP1 is 10.0.2208. It is possible, that the issue occurred during the upgrade process from 10.0.2206. Clean install of 10.0.2208 solves the problem.
Just one more question. Did the Avast uninstall resolved the issue with VirtualBox or was it necessary to re-install VirtualBox as well?
Thanks.
Really, after Avast uninstalling (avastclear.exe I tried also) I had to use VB installation recovery.
Avast uses VB-code to implement the Sandbox sevice. Obviously, some of the modules or their registration data (actively used COM-technology) came into conflict with VB-infrastructure. Your developers need to be more careful when "VB is near".
These problems led to the loss of my working time. Various experiments would only aggravate it.
Don't worry, I'll probably be back (maybe tomorrow).

Thank you. Sorry for my English.