I am using Version 5.0, build 19094 (12cba6f), and I just began having issues while trying to change color class rating. For the record, these are RAW files off of two different Canon 5D Mark III cameras, and the files originated on SD Extreme Pro 32GB cards. Initially I import by copying the files straight from the SD to my desktop, then I take those RAW files into Photo Mechanic. Like many folks, I cull in PM, then I import those photos into LR. While I was culling last night, I was doing my usual 1 (purple) color rating. Of course I changed my mind many times as I'm going through my process and when I press 0, or even if I manually choose the color rating to 'None' by right clicking, the photo file name becomes red and the file is no longer able to be imported into Camera RAW or LR...it essentially becomes corrupt once the metadata is changed. Keep in mind this wasn't in every photo. This also happened again once I had all the photos chosen that I wanted to edit...originally had them color rated, then I wanted to change all their star ratings. 1/4 of them became corrupted. I then had to pull the RAW files off the memory card and choose all them to be imported into LR, outside of Photo Mechanic. Once I did that I was able to edit the file in RAW or LR...none were really corrupted, except after whatever Photo Mechanic was doing to them. Hopefully this makes sense and I'm doing something strange...but I've been using this process for as long as I can remember. Also, for the record, for weddings I go through a more extensive backup prior to culling by copying the files onto multiple drives. This particular shoot was just a practice shoot with a friend, but I'm so thankful it wasn't 800 or more culled photos that had problems...as this small batch of about 90 photos, 18-20 of which became unreadable and I had to search and copy again from SD into the folder to import to LR. Thank you for the help!