Hello, here with the zipped versions of both 2.75a and 2.76RC3 the add-on Sapling Generator works as expected when saving and loading tree presets in an old .blend project (made with v2.69) as well as in a brand new file. My current environment is i7-720Q, Windows 7 Pro 64bit, 8 GB RAM, Nvidia GTS-360M 1GB VRAM. Does the user have the rights to read/write on the \presets folder inside the add-on ...\2.75\scripts\addons\add_curve_sapling?

It seems that that is the problem, the folder is read-only, I can't believe I never thought of that. Sorry for the erroneous bug report.

The problem is that Windows won't let me make the folder not read-only without making the entire program files folder read-only (which I am not ready to do quite yet). I will see if I can dust off my Python and modify the script to save in a different location.

Peter, that's the reason why I don't install Blender but instead I use the zipped version so that I can set the rights I wish on the unzipped folders.

Therefore, I don't think this can be really considered a software "bug".