The bridge tool may have set your face vertices to point directly forward, making the faces look like they are artificicicieded...
Import and export to and from Z kinda prooves it as the program will re evaluate the normals on import and hence when exported its fine.
Try BennyK's suggestion it should sort out the issues.
Chris (formerly R@nSiD)
When the power of love overcomes the love of power the world will truely know peace - Jimmy Hendrix
Winner SM VFX Challenge 1
3rd Place SM SteamPunk Challenge (May 2007)