Help exporting ePUB! "Error formatting image!

Hello!
I’m new to the forums, I’m a first year design student from Portugal who’s struggling with doing an ePUB with the “Digital Publishing” mode on inDesign.

I have this first page where, on roll over, the images appear faded, and then they send to other page of the document. It’s kind of a menu. All seems right on SWF preview.

This menu appears on the other pages as well, but on those page, on roll over, the images move slightly to the front, going back to their original position once the mouse rolls off. All works well also on SWF preview.

However, when I’m exporting for ePUB (Fixed Layout), it starts generating PNGs and after a little bit it shows 13 errors saying: “Error formatting image “x.PNG”. System may be low on memory or disk space.” Which is weird, since this Macbook Pro is only 8 months old and I have most of my files in an External Disk.
So, when I try to open the ePUB on iBooks, the hyperlinks work well, like, linking through the document, but 1. the faded roll over on the first menu doesn’t appear 2. the images don’t roll back in the mini-menu that appears in the other pages

So my question is: is this error generating the PNGs related to the fact that some functions aren’t working while I’m viewing it on iBooks? If you think so, how can I solve this?? If it isn’t, what can I do to solve it anyway?

Thank you all for your time!
And excuse my poor english!