Im pretty sure the p4 3.0ghz CPU core is supposed to be 1.55V... I dont know much about how this will affect your system, however overclockers usually raise their core voltage so i can only assume this might slow down your computer a bit and you will probably notice performance issues. You might want to get your power supply checked out... perhaps try another one and see if your problem is fixed.
edit: you can read an article about voltages here...
http://www.cpuplanet.com/features/article.php/1690721