So a search around Stack Exchange and days on Google hasn't rendered any solution. You guys are pretty much my last hope short of restoring my Mac, etc.
I'm attempting to restore iOS 4.3.2 on to my iPhone 3GS, currently running said version. The issue occurs on modified and legit firmwares.
Shortly after attempting to do so, I'll get a message: "This Device isn't Eligible for the Requested Build" and the restore fails. Searches show a common theme of people who have modified their Mac hosts file, prohibiting or modifying the Mac's connection to gs.apple.com. Be it a hash or removing the entire entry, neither has any effect on the issue, even following a restart or forced cache flush for the hosts file.
Since it's a system-wide modification, a new user shouldn't have any effect. I've also compared the basic entries to a known-good hosts file and nothing is missing or broken.
Hopefully you've got some answers!