Hi,
In Blender can i import obj files (reiners website) and export them as collada without known problems?

None that I've seen. I only have limited need for this tho. I have some old objs from a friend of mine that I've imported just fine, and I tested the colada import/export for someone else.

Only thing I've noticed is that you need to make sure that your loc/rot/scale has been applied, because it'll clear on the export of colada.

I know that you can import .obj files into Blender just fine as I typically have had no problems doing so as long as I have the right add-ons enabled and such.

I don't know anything about Colada though. I would say try it as I read that it is supposed to be an interchangable file format. I don't know if that would include Blender also.

Hope this helps!

before i do anything, how do i load the obj file with materials/textures loaded.
IT doesnt do this automatically as I have .obj, .mtl and .jpg.

I just get the solid shape without textures. I read you F5/F6 and load the textures manually but F5/F6 doesnt do anything in 2.57

I have not used the .OBJ importer in 2.57, but the old one did materials and textures just fine. ( I don't have any files to test at the moment).

One thing to check is that your pathnames for materials and textures actually match the files.