Personally I don't think you're issue has anything to do with "bump mapping"...
Wrong... Please note, I'm talking about with DETAILED TEXTURE disabled, ONLY using bump mapping on the un-detailed terrain! It looks totally different!
My gamma has been default ever since I switched to an LCD monitor some years back. Across various updates, various video card changes, I have never had to tweak my gamma.I shouldn't have to tweak it just for the game to be playable, hence the original post still stands: it needs to be toned down.