I just restored my FalloutNV files via Steam with a view to going through the F&L guide as I have just done with the C&PD guide.
First thing that I did, since I already had all of the steps before done, was to clean the esms.
The actual cleaning went without a hitch, as it should, I've done it with all the Bethesda games before and the instructions are very clear in the guide anyway, an idiot could follow them. I actually cleaned ALL the dirty esms and verified with LOOT that they were in fact good-to-go. Next step, start the game, just to be sure. This is where I noticed something odd immediately. Usually my moue cursor becomes visible after the first screen and I can either hit ESC or click with the mouse to advance through the loading screens quicker, this time no cursor and ESC wasn't doing anything. Finally I got to the screen with the helmeted character brandishing his pistol, but no menu appears, just the same screen and the music continuing.
I started FNV via MO and by the default exes, both the launcher and the main game directly. I also tried with and without the 4GB patcher but still no go. Each time I used the launcher version I checked the 'Data Files' option just to make sure all the esms were being loaded but still no go.
To verify that it was something to do with the cleaned esms, I restored my backups and ran the game. No problem, the cursor appears, I can hit ESC to quicken the load screens and the main menu appears.
I am at a complete loss as to why cleaning them would do this, any ideas?