Power supply overheated, is still ok ?

Last night my computer smelled funny, a bit like burning rubber. Upon further sniffing out today, there were no strong odors from anywhere, but I could smell the remains of the odor coming from the power supply, which is a silent (fanless) supply I bought 2-3 years ago. Running for a 45 min or so today the smell has not returned. What kind of risk am I running if I don't replace the power supply now, but stick with it until the smell comes back ? Is it likely to damage any other components of my system ? Also, I monitor my motherboard, cpu and video card temp's (GForce 8800GT, Core2 Duo at 2.6MHz, DK Lan Party) temperatures and they have been okay running with the case open and no case fans. (The CPU and heatsink have a fan, and the video card has its own fan). If I close it up and run a case fan I might keep my power supply cooler thus preventing future overheating, but I am still wondering if it is dangerous, or if my PSU is definitely on the way out.