This sometimes happens if you are doing spreads, and the artwork on the right hand page actually begins on the left hand page. For example, you might have two pages side by side, and on the left hand page, you might have a picture box that runs onto the second page. Sometimes, the second page is interpreted as being empty, as the picture box is interpreted as being on page one. There are several workarounds for this, the simplest of which is probably to use step & repeat to duplicate the artwork with no offset, and drag the leftmost anchor point to begin on the next page.
That's one possibility. Another, of course, is that something on the blank page is corrupt, which is causing the rest of the page to remain unprocessed.
Another possibility I've come across (although some third party software was involved) was an accidental mouse click or keyboard press while a postscript file was being generated. No error was given, but the pages around that point were still blank.