Minecraft Gamerules not working?

Me and my friend were playing Minecraft, and I created a world with cheats de-activated. When I opened it to LAN, I activated cheats, and changed the two game rules keepInventory (True) and mobGriefing (false). But, my items dropped when I died, and a Creeper blew up part of my Mineshaft.

Later, my friend started up a Singleplayer world (with cheats), enabled those two gamerules (to the same as on our LAN), and the same results happened.

I am pretty sure I put the command in right, seeing as I did:

/gamerule [hit tab until I got to the rule I wanted to change] [hit tab until I got to the way I wanted to change it] and hit enter. 

How do I get them to work?

You must ensure that the following standards are met:

1. Cheats are ON
2. You made sure that the 'g' in gamerule is lowercase
3. The I in keepInventory is capital
4. true is not capitalized.

If all else fails, you might have to re-install Minecraft. If that doesn't work, I have no idea what will. Happy Crafting!

For some reason, if you do /gamerule set (example gamerule) then it will of claimed to of done the gamerule when it has actually not, but if you just put /gamerule (example gamerule) then it will work fine.