Bios only detects HD after multiple reboots

I have a Western Digital Caviar Black 500gb 7200rpm 32mb cache HD. The HD was working perfectly for the first 4-5 months. Now when I turn the computer on in the morning the bios does not detect the hard drive until I manually reboot the pc a few times. After that my pc works flawlessly all day long. However I cannot put my computer to sleep or standby/hibernate, because after a few seconds of waking it up I get a blue screen and once again the HD is not detected by the bios until I reboot it a few times. I've tried increasing the time the bios allows the HD to try and boot up to 15 seconds, Ive tried switching sata ports on my mobo, and I've made sure the sata cable is securely connected, none of which has worked. can anyone help me out, I have no idea what to do?

I'm running Windows Vista 64 bit.
Gigabyte GA-ep45-ud3p motherboard
ATI Radeon Sapphire 4850 x2 2gb
e8400 @ 4.05ghz
PC Power & Cooling 750 watt psu
G.skill 4gb pc2 8500

i had a similar problem i had to boot my pc 2-5 times to get it to work every now and again. i coundnt figure out what the problem was so i left it for 2 years it never got worst or better when i upgraded the mb there was no problem
try updating the bios
if you have a spare hard drive try that if it still happens then i say its the mb

it may be as easy as unplugging it blowing out the dust and crap from the mb and plugging it back in..thats worked for me many times in the past

I'm RMAing it back to Western Digital. Thank god i don't have to spend another 80$ on a new hard drive. Western Digital owns, even if their hard drives fail every few months