Operating system: Windows 10 x64
Graphics card: GTX 660
Broken: 2.79b release
Short description of error
When exporting a model as a Collada file, objects and material names that start with some number get it replaced with an underscore. Maybe it also happens on other properties names.
Exact steps for others to reproduce the error
Rename the default cube object's material name to "0Material" and export as Collada (.dae). Now reimport it back on Blender and check the material name ("_Material").