I've put a bunch of mods onto my Fallout 3 game, and they're were and still are working just fine. But now whenever I download new mods, and install them exactly as I did before by unzipping them into my FO3/Data folder, none of them are showing up in the Data Files screen or on Fallout Mod Manager, and they are not affecting the game at all.

I have the Direct2Drive version, but none of these mods require FOSE. (For example, "a Super Jump Mod", "Slow Food Digestion", and others that are nothing but simple .esp files.)

Has somebody heard of this problem before? Like I said, I was loading mods just fine before but now it seems that I can't add any new ones.

Run FOMM as Administrator.

It appears that WINRAR is unzipping the files into their own subfolders under FO3/DATA, instead of putting them directly into FO3/DATA, FO3/DATA/SHADERS, etc.

For example, the files and all the subfolders will go into a subfolder called "FO3/DATA/Superjump." And, of course, that won't get accessed by the program. I have to go into Windows Explorer and manually move all the files from the subfolder back into the data directory.

I have tried using WinRAR manually, and the Wizard, but it does the same thing. I don't think this was happening before. Does anybody know how to make this files unzip where they need to go.

Try drag-dropping the folders from Winrar into Data instead of using its extract button. That works for me.