since it appears that the erroneous mesh is being rendered out as still erroneous, I would say your max file got slightly corrupted.
Select the object, Reset Xforms, export to .3ds, close max
open max, import the 3ds, delete the junk areas, weld any open vertices, reset x-forms, and save as a new file. Close max.
Open max, then open your file you saved out... then start over again on the parts that got messed up
