wtf just happened?

Just 10 minutes ago I walk out of my room, come back in a few minutes later and my computer was off. I tryed turning it back on and all all i got was my power light blinking and no sound of fans or a post.
So i unplugged everything, opened the case and everthing looked fine.
I plugged the computer back in and it started up fine.
I can't think of what it could be other than my power supply. I check my voltages and they are:
CPU Core 1.47 V
+3.3 V 3.20 V
+5 V 5.00 V
+12 V 11.92 V
-12 V -11.95 V
-5 V -5.10 V
+5 V Standby 4.95 V
VBAT Battery 3.54 V
They seem fine too me. So what do you guys think it could be?

AMD64 2800+
MSI Neo-Fis2r
512mb Kingmax ddr400
Sapphire 9800pro 128mb
10K WD Raptor