Taigore's Inventory Saver

v3.0 - MC 1.5.2 / 1.4.7 - Forge 7.8.0.684+
-Ported to Minecraft 1.5.2
-Improved the bag GUI
-Changed name display method
-Added two config options: lava vulnerability of the bag and protection against looting
-General refactoring
v2.2.2 - MC 1.5.1 - Forge 7.7.1.611+
-Ported to Minecraft 1.5.1
v2.2.1 - MC1.5 - Forge 7.7.0.575+
-Ported to Minecraft 1.5. No actual improvements.
-The update seems to have fixed the "unclickable bag" bug on its own. Guess it was the Forge update.
v2.2
-General code refactoring, hilarity(= DISASTER!) may ensue
-Implemented "T" button to shift click everything, and "S" button to switch bag pages
v2.1.1
-Fixed the EndOfStream client crash on server
v2.1 - MC 1.4.7 - Forge 6.6.0.497+
-First release

Caveats

If you happen to die close to your spawn point, either in single or multiplayer, it may happen that the bag is either invisible or unclickable.
This is a bug that I found to occur even in Forge-only Minecraft, even with other entities.
The only known fix is to either reload the world, relog into the server or simply getting far enough from the bag to have the chunk unloaded by the game.
It's not a gamebreaking bug, and nothing you should worry about if you die in normal conditions (i.e. exploring or fighting at least couple of chunks away from your spawn)