Minecraft: 1.3.2
Forge: 4.0.0.237
When using a pickaxe with Silk Touch on an Ender Chest, standard minecraft drops the actual chest (instead of just 8 obsidian which you will get if you do not use a Silk Touch enchanted tool)
However, after installing forge, this behavior changed. Now the pickaxe with Silk Touch breaks the chest (returning 8 obsidian). Silk touch works normally on other blocks I tested it on however, it is only on the ender chest it doesn't work properly.
I did some testing, and tested this with a clean minecraft.jar, then applying only forge, nothing else (and no mods in my mods folder either). Standard minecraft, silk touch works on ender chests as expected, but immediately upon installing forge, the same pickaxe starts breaking the chest instead.
ForgeModLoader-client-0.log