We don't directly support Vista x64 so far, but thanks to FreeRIP users community, and particularly thanks to Indou, we have a workaround to make FreeRIP work on this platform.
Basically the workaround consists on setting FreeRIp work in Vista's Windows 98 emulation.
To do so just find FreeRIP icon, right click on it and select Properties menu option. Go to the Compatibility tab and check Run this program in compatibility mode for. Select Windows 98/Windows ME.
Then press OK to save these settings. Now FreeRIP should work fine.