Hi everybody,
We have further investigated this issue and can confirm that the reason for it is a change in the default value of the IoBlockLegacyFsFilters registry key value. While the blocking of legacy file system filter drivers was optional, it is now the default since Windows 10 Insider Preview 17063. Because Boxcryptor uses a legacy file system filter driver as part to provide the virtual disk, it cannot be mounted and causes the application to crash.
As described by vdasdb, a quick workaround is to allow loading of legacy file system filter driver. After you change the IoBlockLegacyFsFilters value to 0 and rebooted your computer, Boxcryptor should work again as before. More information how to change this value can be found in the link provided by vdasdb:
https://docs.microsoft.com/en-us/windows-hardware/drivers/ifs/blocking-file-system-filter-drivers
I can ensure you that we are working on a real "fix" for this issue and we will make sure this workaround is not needed anymore until the final release of Windows 10 1803.
Best regards,
Robert