Wrong images appearing in project window / timeline

Question

I'm doing a SIMPLE slideshow project for a frient. I've got a file folder of images that I imported into CS5. In the timeline the correct images are not appearing when placed from the timeline. Even in the Project folder most of the images are not what they are in explorer. Most, when opened in the Source Monitor are the correct image, even though the wrong image is appearing on the timeline, but even there many are not correct. What is happening is that the image of about 15 of the 105 imported images are appearing in the place of all of the other images. It's like something is cached, and the appropriate linkages aren't being made.
What's even more frustrating is that the ONLY effect applied to all of the impages is Scale to Frame. There are no transistion. Nothing.
What simple solution is there for images not importing into CS5 correctly?
ARGH!!!!!!!!!!!!!!!!

Answer 1

Thanks for that suggestion.  It DOES work!  However, it is time consuming since I'm working with over 1,000 images.  Instead, I was able to discover the following solution:
The culprit was the magic checkbox under Edit -> Preferences -> Media for "Write XMP ID to Files on Import."  This setting writes a GUID to all media imported into Premiere for use with all Adobe apps.  I actually found the reference to it in an After Effects forum.  I didn't fully understand exactly why this is useful when I'm only working with still images.  My guess is that somehow these GUIDs became crossed over.
I disabled this checkbox, deleted all references to the affected media, and deleted all cache files, including all files under C:\Users\Username\AppData\Adobe\Common\Media Cache.  I then reimported the originals of my source files from my network attached storage (SO thankful that I moved them offline without touching them).  Viola!  Everything works.
It was critical that I made copies of all of my data to my NAS.  Adobe actually writes this GUID for the XMP ID to the file itself, which changes the modification date of the actual file.  So, I guess the error will follow the file wherever it goes (in an Adobe application) unless it's resaved in PhotoShop to correct the error.  Luckily, the files on my NAS were untouched by Adobe, since I made copies to work with locally.  Only the local files were affected.  Once I disabled the checkbox, then Adobe no longer attempts to modify files on import and leaves them intact.