poser 5 as an obj converter. YMMV. :-)
Problem is probably to do with the number and type of materials:
1. Open the obj file in wordpad (or somesuch) and do a find for "usemtl".
Note the unique names and how many there are in total. (e.g usemtl metal )
(These may not be unique in the file. You will need one entry in the default shader for every usemtl in the obj file).
The number of unique names in the file is an indication of how many discreet materials there are.
2. So now open up the internal network of the object. (r-click on the node)
To get a quick result - make a power fractal shader (turn off displacement internally) and connect its output to the multishader shader inputs.
You will need one per usemtl entry. if you don't have enough then it will probably crash.
3. So now you would have a single power fractal and lines from its output to the first N shader inputs on the multishader
(where N is the number of usemtls in the obj file)
Now should render.
If you replace the Power shader with a Default shader and choose images where there are texturemaps, and set other material aspects then you can slowly refine your way to the look you want.
There is a limit - the multishader only takes 16 shader inputs. So you need to stack them if there are more. (link to input)
A better obj converter might make a file with the minimum number of usemtls. I.e. each one appears only once. This will help you to get easier results.
The image below shows the internal network of an object with two materials. But used twice each in the obj file.
One shader is connected to a fractal and the other is connected to a default shader (which internally refers to a texturemap). The second also has a fractal being aded on top of the texure map (in this case adding rust stains)
Oh yeah - once your happy - rclick on the object top level node and save as a tgo. (for next time)