Guest Tools cannot be installed on a Virtual Machine with the following output:
Parallels Tools 6.5.23234.964887 Installer started. 2014-03-13T17:39:26+0400: Failed to setup console printk level. 2014-03-13T17:39:29+0400: execCmd: ./installer/pm.sh check_guest_tools 2>&1 
/var/log/parallels-tools-install.log, the following or similar messages can be found:
2014-03-13T15:53:39+0400: Err ftp://ftp.debian.org stable Release.gpg Could not resolve 'ftp.debian.org' ... 2014-03-13T15:53:39+0400: Error: An error occurred when downloading required components for Parallels Tools installation. - gcc - make - kernel sources
The VM has incorrect network settings.
The installation of Guest Tools requires the access to external resources (OS repositories) to download kernel headers in order to compile the suitable drivers for the current OS. Therefore, the VM should have correct network settings and be able to access the Internet.
Apply proper network settings from inside the VM.