Problem: One of the recent updates seems to delete the Vendetta.exe file.
Only a few updates loaded, so maybe it was one of these: 1.8.238, 1.8.238.1, or 1.8.238.2

Workaround Solution:
Make a copy of update.rlb.
Rename the copy to Vendetta.exe
Run VO as usual via the shortcut.

Background:
Downloaded VendettaOnlineSetup.exe for Windows yesterday (2012-12-20).
Ran it today to install VO.
Ran VO, it loaded one or more updates.
Clicked "Play Vendetta" and that worked.
After reviewing & adjusting the Options I tried to setup a rule for Vendetta.exe in the Logitech (SetPoint) mouse software and couldn't locate Vendetta.exe.
Exited VO and tried to run it again via the shortcut and sure enough it gave an error because the file no longer exists.
Verified that Vendetta.exe did not get put into the VirtualStore folder.

Installed VO again. Didn't bother to uninstall first.
Ran VO via the shortcut.
Clicked "Cancel" instead of "Play Vendetta" after the updates loaded.
Checked for Vendetta.exe and again it was missing.
Used the workaround solution listed above.
Ran VO and the .exe did NOT get deleted this time.

Anyone else with this problem: I've had the .exe deleted by my antivirus because it is perceived as making changes to your computer. You may want to check your antivirus settings relating to VO if this problem occurs.