with this image it really looks that it is 2 or more faces on the same place, that is the problem when importing from other app, you have to know every setting for a good import, good luck.
maybe it is a "normals" problem or try put a UV mapp modifier. If it is a normals problem put on it a normal modifier and flip the normals. You can use a camera correction modifier as well, some walls look very inclined.
one problem that i have whas the snap change, it works different from V6, but it takes time to get use to it, even i heard you can fix it like V6, anyway, the improve in mental ray is great.