The program is displaying the wrong smart previews.
It sounds like catalog or smart preview database/subsystem has gotten fouled up. But I'm not sure what you mean by:
"When I open the actual file it shows a different image than it does in my catalog."
Which file are you opening, and how are you trying to open it? Photo source file? actual smart preview dng file? ...
My guess: regular preview is wrong, so what you see in catalog is not representing the true photo/source file - could that be?
First thing to do is:
* context-click photo and choose 'Show in Explorer/Finder' - make sure source file matches what you see in Lightroom. If not, then delete your catalog Previews.lrdata folder and restart Lightroom (standard previews will need to be rebuilt).
* If it does match, then run script 'Show Smart Preview in OS' from MiscScripts distribution (free by me). Open smart-preview dng in app of your choice - is it same as catalog photo? If not, then delete your catalog Smart Previews.lrdata folder (you'll need to rebuild smart previews).
If that don't get it - do tell..