For your understanding:
- There's a switcher (or in fact, there are several) to switch between (sub)versions of the game.
- There's a mod checker tool (chkmods v1.09a) that can help you fix issues with mods.
Hm, that'd be the version of Check mods, not the switcher...
I wanted to know whether you are using the 'IL2VersionSwitcher.exe v.12 that came with AAA 1.1, or the switcher B16Enk created ('Switcher.exe')... but, probably you are using the first one.
As for the error you are getting when switching, is it excactly like you said "\4.08 Mod ON"? Or maybe '4.08 Mod ON (NO 6DOF)'?
You can try and delete/move the 'IL2VersionSwitcher.exe' file and the file 'currentversion.txt' from your IL2 folder, and the folder '_Game Switchers', and then run ChkMods again, and let it download the missing files. (I cannot understand how/why ChkMods.exe cannot fix the issues right now...)