Sounds peculiar. first thing I'd do though is get rid of (or at least rearrange) the try...catch block - you should only use them if there is no way of knowing whether an operation will succeed (like for example trying to access a CD drive without knowing if there is a disc in it). This certainly isn't the case for lines like oNode.ImageIndex = 3. Maybe it is when you are testing the ToString of the drive - if that is the case the try..catch should be wrapping just this one line.

Can you elaborate - when you say the images show rarely.. have you been able to identify any patrern as to in what circumstances the images do show up. As for the picturebox showing only a shadow of an image - it should really be a separate thread, but can you give us a screenshot of what it looks like and another of the actual image as it should show?