I was having issues since installing TTW 2.4, so I went back to the drawing board. I pulled out my FO3 retail disc (the GFWL version), redownloaded my DLC from GFWL, reinstalled them all, and finally patched to 1.7. Now every time the installer pops out the same error message when it hits Fallout3.esm.
I have already tried using my key to claim on Steam, but surprise, no success. I rebooted, still got the error running the installer. I never had this error before reinstalling the files (including a 2.4 install which was suffering infinite menu load, hence the attempt to provide fresh files) and used to successfully run 2.2. Anyone have any idea what's going on and how I might resolve it?