Well... yes... I was thinking along those lines but have been unable to identify exactly what is "corrupt" about them, especially as all of my other applications, including the Internet Browser (whcih obviously displays the jpeg above), work.
Since Chris has now confirmed he uses a third-party JPEG loader, I suspect it has to do with the JFIF (which is what JPG really should be called) header and I can only assume that the failing ones do not have them (and the loader expects and when it doesn't find it, cacks itself).
Loading them into ThumbsPlus (which is what I use for mass displaying and alteration of images - other people probably use something like ACDSee or IrfanView) I basically just resave them and on the JPG option screen ensure that the Suppress JFIF Header box is NOT ticked and that seems to rebuild it successfully. These rebuilt "failing" covers will then happily display within Wincab.
The only problem is stepping through every jukebox page in the first place and identifying them quickly before the crash screen appears. I'm done now thankfully.