I almost always use open meshes and I never have problems with textures displaying. I can quite safely rule out an open mesh being the problem with 98% certainty. I have no experience with importing of any kind so I can't help you much with that, but only guess. One such guess is to make sure that, upon importing, make sure that the texture is imported as well. Textures generally need to be a power of 2, but I've read of others not using the power-of-2 rule and still not having problems.