I've been having exactly this problem with miniscule font sizes on my invoices for a few months now -- not all over the invoices, but in certain text areas. I've mentioned it at a couple of the Wed. board sessions with eBay.ca staff, but I don't think they understood that the problem is not one of adjusting the view on my computer screen.
The same thing (shrunken fonts in odd places) has also happened on a few other pages of mine on eBay. One day they all went back to normal, now they're tiny again. I've more or less given up on it, in the hope that it might eventually all revert to normal permanently.
I don't know what to say that might help but perhaps if another seller were to report this, it might get some attention. I think there's been so much monkeying around with this site that some things got broken in the process.
Please post an update here if you get any answers from eBay other than the usual "adjust your screen settings" nonsense. 
