I'm wondering if perhaps you have the entire text of the book in a single xhtml file within the epub. If that file is larger than about 300Kb (I think... if someone knows more accurately, please chime in), some readers will choke on it and fail to display the large file. Whereas, PC-based readers generally don't have this limitation.
I'm not sure that explains the four blank pages, though.
Anyway, if you do have a file larger than 300K, you can split it up easily using Sigil, and see if that helps.
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