I can see edges of surfaces around the grey part. It seems to me like they just turned transparent rather than disappearing. I would check all of your appearances and make sure there isn't a transparent one that somehow got applied to those invisible surfaces.
The picture looks like an assembly, or is it a multi-body part?
Run a Check (Tools/Check or Evaluate/Check) on the part. (I usually choose the "Stringent" option as it doesn't seem to be much slower and I assume it catches more problems.) Faces that disappear are often a sign that the part has become corrupted. If so, try to come up with a way to stop it from being corrupted or a way to fix the corruption.
Sometimes the part will check OK but faces disappear or display incorrectly. It seems like this is an indication that the part is really corrupt, but SolidWorks can't find it yet, or it is flaky and may become corrupted with later operations. In a few cases I have been able to make such parts better, but I don't have any general advice. Small faces and fillets seem to be the likely culprits.
All of the above assumes that it isn't just an appearance issue, as Jamil suggests it might be.
First off, I would like to thank both Jamil and Jerry for the prompt feed back.
I performed both the geometry analysis and the part check as Jerry suggested with no glaring results, so I went back through my feature tree.
I had converted a sketch at the parting line of my sink details and used them to make surfaces. I offset those surfaces and the cuts down to the offset surfaces are fine, while the cuts that were made to the parent surfaces resulted in the see thru surfaces.
While I could not directly select the unseen surfaces, I could place fillets on the intersections that the missing surfaces shared with normal surfaces.
I am going to try a different approach to the cuts that are producing the unseen surfaces and I will reply to this post when I figure out how to fix this.
I have fixed my issue, but I don't know why it did what it did.
I deleted the two up to surface cuts that were at fault and re-applied them later in the feature tree and the invisable surfaces did not return.
SolidWorks has been freezing and crashing a lot today (4 times), so it may be an issue with my pc/graphics card. Thanks for reading this and trying to help me out.
Anytime you have issues with odd things happening in the way things look, you should check your graphics card driver and make sure it matches the driver that has been approved by SW. http://www.solidworks.com/sw/support/videocardtesting.html
I actually fell into this trap yesterday. I've been having a few minor video glitches, and I never though to check my driver as I always make sure I install the approved driver. Low and behold I check the support site and I was using an older driver. I updated to the new version, and my problem went away.
I will check that first thing tomorrow morning. I too try to be vigilant in keeping up with my drivers, but it is easy to forget sometimes!
Thanks for the advice!
Well, it's not even a matter of keeping the latest driver. Sometimes the one approved by SolidWorks is an old version.