Hp 4L laserjet page feed problem

Hello. My HP 4L has worked fine until yesterday. I load all pages one at a time manually (my preference) but all of a sudden as it was loading a page it started making a terrible groaning sound and would not take the paper. The error light came on, so I checked the pathways and found no paper, I pulled the toner cartridge (and even put a new one in), but it still groans loudly and will not accept paper. BTW I use the "straight through" paper feed instead of having it curl back up into the tray. Any advice? Thanks.