Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).
Do NOT click the Reset button on the Safe Mode start window.
If the menu bar is hidden then try to bring up this toolbar to see if it works from there.
Press the F10 key or tap the Alt key to bring up the hidden "Menu Bar" temporarily.
Did you try Safe Mode?
A good place to discuss issues with Firefox nightly builds and Firefox beta builds is at the MozillaZine Firefox Builds forum.
You need to register on the MozillaZine forum site in order to post at that forum.
Thank you for your answer, But I should have been more descriptive, I am able to print in normal /windows mode of Nightly but I am unable to do that in Metro Mode. And there is no help either by pressing 'F10' or 'Alt Key' in this mode. And I am also unable to start Firefox Nightly (Metro Mode) in Safe Mode.
I did try your answer in normal/windows mode that works very well in that mode, but no good for Metro Mode.