printing blank pages

We have a HP Laserjet 5000 N printer with the latest drivers installed (version 6). It periodically throws out an extra blank page at the end of a document. This happens with HTML pages, occasionally Word documents and HTML e-mails. The strange thing is that it doesn’t do it all the time, it might not give off a blank page for days or it might give off dozens of blank pages in a day. Any advice would be greatly appreciated.