Yup - now I know exactly what you mean.
Unfortunately, I don't sync with Exchange so I cannot help much. I can suggest a couple of things - notice anything weird about the subject lines, like perhaps the ones not showing starting with a special character, or a space, instead of a normal letter? Is he subject line perhaps too long to fit into the allotted space on your calendar view? Or is the color of the font different from normal, or even the font itself?