Minecraft 15w45a, Minecraft 15w46a, Minecraft 15w47c
OS: Windows 10 64 bit
When you try to place blocks where a floating marker armor stand is, only certain blocks like redstone, string, or fences can be placed. All other blocks flash briefly and then disappear.
Steps to Reproduce:
1. Run the commands
2.You can place a stone block in the 1st armor stand, but not in the 2nd.
3.You can place redstone in both armor stands.