Unbelievable! Thank you so much Jellby! I would never have guessed.
So Adobe uses the compressed size instead of the actual size of the files to determine pages.... What can I say...
What do you use for zipping, by the way? I just used UltimateZip with no compression, so that I would have no problems with the mimetype file. It does not seem to offer many levels of compression, just "fast", "normal", etc. I tried with normal compression and got the cover on page 1, and 56 pages of book...
So to anyone else having the same problem: Either keep your cover page <=1kb or compress!

for answering what to me was a great mystery!
Was the rest of my code okay? I'd like to hear any corrections from you ePub pros!