Virtual machine's (Guest OS) screen area is not displayed on external monitor after entering Full Screen mode with 'Use All Displays in Full screen' and 'Use Mac OS X Full screen' options enabled.
Mac OS 10.9 Mavericks has introduced a new feature, "space per display", which is fully supported in Parallels Desktop 9 (starting from the revision 9.0.23136.932290).
There are three options to use multiple monitors in Parallels Desktop on Mac OS X:
Upgrade to Parallels Desktop 9 (9.0.23136.932290 and later) or to Parallels Desktop 10 the latest version: Parallels Desktop menu -> Check for Updates...
Turn off the option "Displays have separate Spaces" in System Preferences -> Mission Control. Please note that this would affect all programs on Mac OS.
Turn off the option "Use Mac OS X Full Screen" in the Actions (or Virtual Machine menu in Parallels Desktop 9) -> Configuration -> Options -> Full Screen.
Log out and then log back in to your Mac user account
- Start Parallels Desktop and check the issue