models are non manifold but as far as i know thy are ok

iv been printing from shapeways for a while but for some reason im having issues on some models. attached is one of the objs. the model is not too small its not too thin. no holes in the model. just 2 simple oval ring like shapes. can somebody help me out? thanks everyone

error i get uploading
We're unable to process this file. Check your file for errors and click 'Update File' to upload a new version.
Model is not manifold.
Model failed during repair.

Not sure yet what the issue is, but just load it into (free, cross-platform) netfabb studio basic and immediately export it to another obj file (using "Export part" in the "Part" menu). The resulting file uploads flawlessly, but the model is very small if one chooses millimeter units. A comment at the top of your file suggests it is in centimeters, so you could either use shapeways' SCALE option after upload, or use Part->Scale in netfabb to enlarge it by a factor of ten.
Apart from that, the most obvious difference between the original and rewritten obj files is a bunch of "vt" entries in the former, with one parameter a very large constant number and the other zero. These are completely absent in the "correct" file - but I am not familiar enough with obj format to know their significance. Also, a number of "vn" (vertex normal ?) entries have been recalculated, although netfabb did not produce any warnings about the original model.

I can't look at the .obj file right now, but if you have pieces that check out individually but the model fails as a whole, it could be that two different closed shells are exactly sharing a vertex. An example would be two overlapping cylinders that share their central point on two of the end-caps. I've seen this happen frequently and the fix is as simple as offsetting one of the objects or vertices by a tiny amount.

awesome thanks guys. never used that program b4. ill take a look. im surprised iv never run into this b4. thanks again for the help