Linux bubastis 3.10.25-gentoo #10 SMP Thu Jan 30 22:17:35 UTC 2014 x86_64 Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz GenuineIntel GNU/Linux
01:00.0 VGA compatible controller: NVIDIA Corporation GK107GLM [Quadro K1100M] (rev a1) (prog-if 00 [VGA controller])
**Short description of error**
The Undo operation sometimes affects more than one previous operation. This can wreak havoc on the properties adjustment panel of an addon.
**Exact steps for others to reproduce the error**
Start with the default cube.
Make a linked duplicate (alt-D) and drag it off to the side.
Add an array modifier to the original.
In the mesh panel, use the  button to make a single-user copy of the mesh.
In the modifier panel [Apply] the modifier.
Notice that the array modifier has been restored. (this is correct). Unfortunately, the mesh is no longer single-user (it undid an extra operation which is incorrect).