I updated a Windows 2008 R2 VM with the same optional update and I can access it after reboot.
Try to reboot your VM machine again and see if you can get your access back. If did not work, then you will need to snapshot the VM's boot disk (for backup purpose if something goes wrong), delete the VM machine but keep its disks. Attach the boot disk to a test Windows VM machine as an additional disk and replace
D:\windows\system32\drivers\netkvm.sys file with an older version file from test machine (I assumed
D: will be drive name of the attached disk).
Detach the disk and create your Windows VM again using the repaired boot disk.