empty output issue

Hi, I'm new to shapeways and I wanted to print out a ring, I uploaded a prototype of my ring (because it was unfinished), in multiple file formats to shapeways and they all gave the same error, empty output. But when I checked my model, all the normals are correct and I made sure to use a boolean operation on all parts. And finally, I used Netfabb to check and repair my ring. it came out correct, with no bad edges, 1 shell, no holes, positive volume, surface is closed, surface is orientable, and I exported it from Netfabb and uploaded it again. It still gave the same error, empty output.
I'm running out of ideas here, can someone here just take a quick look at my file and tell me what is wrong with it?

I'm not sure how you managed it, but it looks like every triangle here faces both outward and inward.. essentially, your ring is hollow, with a wall thickness of zero. The net volume of the whole thing is zero.

What did you draw this with? Also, what are the dimensions?

it was done in 3dsmax 2011, I'm not sure how it became like that, could be the export settings, I need to check 3ds's STL export settings.
this was my first time exporting to STL.

the dimensions are 21.017mm 6.228mm and 21.193mm in 3ds max, with a volume of 0.31cm3

edit: I checked the stl file in 3ds max , I didn't see any 2 side faces.

The software exported your file in units of INCHES instead of millimeters.

There are three ways to fix this:
1) Convince your software to export in millimeters
2) Open the STL in Netfabb-Basic and use the command Part/Scale to increase it by a factor of 25.4
3) On the Shapeways Upload page, select Inches.

Note: you'll want to use only ONE of these methods to fix it

I don't use that particular software package, but I think somewhere else here on the forum, someone else had the same problem.

thanks a lot, that solved it.