I would also try to improve the accuracy of the geometry in CATIA. When you export it, you discretize the surface, and if the discretization is too large you can have errors in the geometry.

I have found that importing as .stl helps sometimes, besides the options that have already been mentioned

Verify the tolerance  in the ICEM options. Sometimes  it is set too high and some holes or  no soft curves can arise. The repair is an option.  Although the CATIA interface to ICEM is a native feature, I do prefer use parasolid format. There are less errors in tolerances and geometry reading. And binary format else, because it is faster to read. 

Are you using a CATIA-plugged-in interface or are you using file transfer? For the latter the best option is to use the native CATIA format (at least V4-format). Other formats like IGS suffer from limited accuracy depending on the size of your geometry (10^-6 times the largest dimension).

Best check your geometry within CATIA for water-tightness. This can be achieved by creating a volume from the surfaces. During this process you can see any misalignment of surface boundaries and you can correct this in the CAD system directly.

Although ICEM is not per se depending on a watertight BREP surface, practice shows thgat this is also there favourable to avoid meshing problems, either holes or badly defined projections which cause some handwork to be eliminated.

Try different format to improve your imported geometry in ICEM CFD, for example try igs, iges, sat...etc to find the best one for your problem. In addition, in CATIA see the settings under every format that may help in improving the export geometry from the program.