My guess is that Mint can't find the Mint partition and that running update Grub
would likely fix the problem, but that's really a shot in the dark; it would help the see the error messages
Perhaps you could take a photo of the errors and attach it to a post. I've found that setting my camera to "shutter priority" makes for the best photos of monitor screens.
To attach a file to a post, click the "Go Advanced" button at the bottom of the "compose post" window (just to the right of the "Post Quick Reply" button). The attach file dialog can be found there.