OK, several problems have been solved. Thank you Chuck!!! Now I can upload a zip file without the previous errors.
But... after upload and unzip a zip file, after the page shows all is correct... simply, there are no images. I have tested with several zip files and diferents sizes, but nothing. There are no signal of the zip file, or images, or errors... nothing. I'm going crazy because I think all settings (for PhotoPost and php.ini) are fine. But it is clear that something is wrong.
If you think is necesary I can send an email to you with the info you need to solve this.