I have heard of this problem before.. the nv4 thing is referring to your nvidia drivers, However there is nothing wrong with your video drivers, some other problem is causing this loop issue. By chance do you have spy sweeper installed?
If not a friend of mine has this same problem.. we goggled numerous time to find a step by step fix and this is the one we found to fix it...Hope it works for you.. (I'm not taking credit for it hence why I'm quoting it)
Originally Posted by zeno
first download DRIVER CLEANER PRO. NOT drive cleaner pro. and install it. dont use it just yet. go into add/remove programs click remove nvidia drivers,and a small screen will come up, only place a check mark on (remove only the following) check mark nvidia display driver.remove it. when done go into safe mode when in there read the instructions in driver cleaner pro. to remove nvidia display driver, scroll down the list in driver cleaner pro for (NVIDIA) only NVIDIA and left click it. then on the right click start. a message will say are you sure you want to remove display driver files or something like that. click yes. when its done it will show you the deleted files. exit driver cleaner pro. if its a dell system you have. then when the above is done. click start then click search all files and folders, type in nv4 click search and it should still find nv4 disp.sys/32. and nv4 sys32 miniport. if you see these remove them. their from dell old display drivers which im sure are conflicting with the newer nvidia display drivers. driver cleaner pro does not notice these files so its best to search them. when removed start the pc up and install your new display driver. hope it works for you.