Why don't imported photos show in Lightroom?

Question

I imported a folder of approximately 170 pictures into lightroom using the same process I have been using for a month.  the files are a combination of canon .cr2 files and the matching .jpg files that go with the .cr2s.
After the import completed lightroom showed zero photos in that folder.  I immediately panicked and double checked that all the files really did exist in the folder via windows explorer. 
However, if I go back and try re-importing the files the import function shows all the files as having been previously imported.
I have tried the "synchronize folder" process, and it first shows the files as '170' to import, but after the synch function complete it shows 0 files processed.
Any ideas why lightroom refuses to show this particular group of folders?
I suspect it is something either really simple or the library on my system is messed up due to corruption.
If the library is messed up how do I go about rebuilding it.  These photos are critical to me as they are headshots of an actress.

Answer 1

THANK YOU, THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU,THANK YOU!
I was panicking because I spent an hour with my friend/client going through these 170 shots cropping, minor tweaking, and picking out the best for further work.   I managed to reload the pictures, but thought I had lost all the post prep we had done.
You nailed the issue dead on and I've found the files with all the post prep catalog info.
If you were here I would kiss you!
And by the way, did I say THANK YOU!!!!
Thanks, Bobw