That's a UI bug, sorrry! You need to clear Engine Path, set the Export Type to SMD, then set the Engine Path again. That will be fixed in the next release.

There was a changelog note...it was just ages ago. :-)

It's a fair point about saving user prefs. I want to save the old add-on being disabled, but of course any other changes are saved too. I'll just remove the save call; in most cases the user will do it themselves anyway. The worst that will happen is a "missing add-on" warning on the prefs screen.

io_smd_tools.py in the old filename of the tools, back when the whole thing was just one file.

The only job it has these days is deleting itself so that you can't have two versions installed. That's initialised at io_scene_valvesource\__init__.py line 38. Is that script not running?

http://psteamcommunity.yuanyoumao.com/workshop/about/?appid=570#service_providers

There's a slider for the Blender Foundation, who make Blender, but not one for me. Unless I'm very much mistaken.

I see that deleted comment... :) I'm not on the list unfortunately.

Ehwot? I thought you were bone parenting it to the character's armature, not its own! No wonder things went mental when you unparented.

Use the Clear Parent operator but this time choose "Keep Transforms". Then re-parent it to the armature normally.

I assume that "weapon4_0" is a bone on the character model?

It sounds to me like you don't have matching bone names. If you upload the blend I can see what's going on for myself.

If you want to reposition the object, parent it to the armature normally. then the Tools will export its position relative to the armature.

In Source, inter-model parenting is done through bone names. Parenting in Blender has no effect whatosever on the model's parent in Source.

The solution to your problem is removing the bone parent. Why don't you just try it and report back?