This is not the case as spine.exe runs just fine from shortcut. I will try to run with spine.com, I see there is an advice on your website.
it's not working with spine.com. here is the log when I run from command prompt:
Spine Launcher 2.1.20
Windows 8 x86 6.2
Java 1.7.0_06 Esoteric Software
32-bit Server VM
Spine 2.1.10 Professional, LWJGL
Licensed to: *****, *****
Intel
Intel(R) HD Graphics 4000
4.0.0 - Build 10.18.10.3412
JSON export: myobject
Complete.
my command looks like this:
"C:\Program Files (x86)\Spine\spine.com" -i myobject.spine -o "PATH_OUTPUT" -e default.json