i am new to the forum, as well as to producing in general,
heres whats up,
after about 45 minutes of working on a song, when i hit play, no sound will come out.
i dont screw around with any settings,
i only use the samples included in the program, and havent moved there location.
i just dont know what randomly goes wrong everytime !
i tried copying the entire track, and pasting it in a new one, and loading my samples into thte appropriate spots, and THAT doesnt work, the only way i can get sound coming out of the program again, is to start a new song.
hmm sounds like you either have a problem with your soundcard drivers… or, a badly cracked version of renoise? 
does it help to save the song, and then restart Renoise and reload it? or maybe even rebooting your computer? you could try updating your soundcard drivers
What OS you have?
Try:
Mixer -> Master Track -> Pre -> Is The Volume at Zero?
Mixer -> Master Track -> Post -> Is The Volume at Zero?
Do you have Auto Gain turned on by accident? This attenuates your volume automatically if it’s too loud, sometimes this is a problem because your intention is loudness.