I hope you are doing well.
I have seen this with other CAM packages when trying to bring in SolidWorks assemblies. After some research I found that it comes down to what information SolidWorks includes for outside products to read, and of course what they are capable to bring in from SolidWorks. There is a long list of SolidWorks Gold Partner CAM packages that run right inside SolidWorks http://www.solidworks.com/sw/products/engineering-software-partners.htm These takes the experience to a totally other level when talking about SolidWorks assembly machining.
If you are sticking with your standalone Esprit I would think that XT files is your best bet.
Hope you find this helpful.
There is a reason true fully integrated CADCAM from just on vendor makes a huge difference.
You don't get true fully integrated CAM when running CAM inside of SolidWorks because no CAM that runs inside of SolidWorks can create its own Assembly file.
All CAM that runs inside of SolidWorks rides on top of a SolidWorks Assembly file.
I hope that when SolidWork V6 finally becomes available that it addresses this massive shortcoming of the current SolidWorks.
As far as the problem you having, here is what I would suggest.
1. Watch this video and see how easy it is to import SolidWorks Assemblies into TopSolid CADCAM 7:
2. Download TopSolid CADCAM 7 and try it yourself with the SolidWorks Assembly file you are having problems importing into DP Technology Esprit:
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