Im aware that this may be constrived as diverting the Thread somewhat, So in this post and in yours, any further questions can be edited in, rather than posting again, is that OK?
Well a virtual photon is where as Heisenberg stated, the less time looked at a system the more unpredictable it is, and photons pop in and out of existance, borrowing and returning energy. This is also incidently how a black hole evaporates.
If your wondering HOW i know this, i read a book a couple of years back, called 'In Search of Shrodinger's Cat'. Seriously good read.