按照指南一直做下去，运行3个多小时后，最后出现了这样的错误：
*** Error
/image: Prerequisite failed
/image.prerun: Prerequisite failed
/clearDBlocks: Command execution failed
$$path(QtopiaSdk:/bin/content_installer,generated) -clearlocks $$QTOPIA_IMAGE/qtopia_db.sqlite
/opt/FriendlyARM/mini6410/linux/x86-qt-extended-4.4.3/builddir/sdk/bin/content_installer -clearlocks /opt/FriendlyARM/mini6410/linux/x86-qt-extended-4.4.3/builddir/image/qtopia_db.sqlite
*********************************************************
content_installer needs a unique port but it cannot open
port 8688 . Please kill any stale content_installer
instances or use a different port.
You can instruct content_installer to use a different port by
setting the CONTENT_INSTALLER_PORT environment variable.
*********************************************************
请问，这如何解决呢？困扰了我很久的问题！谢谢！
