It may just make those noises while it's working under heavy loads, although that seems irregular for a 500watt supply.
If the warranty is still good, I'd take it back and get it switched with another one, try that one out, if it still makes the clicking sounds, I'd say it's time for a new power supply.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w