Sleep mode and hibernate not working properly

I have a custom built PC that I myself built. I've had it for 2-3 years now. From the time it was built until a few months ago sleep mode worked perfect. When I went to the start menu and clicked the little power button the computer would enter sleep and whenever I wanted to resume my work I would hit the mouse button or the spacebar and it would boot right back up where I left off.

Recently, however, that has changed. Now when I click the power button the computer seems to enter sleep mode but takes about a minute longer to do so. It will also not allow me to power back on with the mouse or keyboard, I have to use the power button. Then once I push the power button, the fans and lights power on but the display, which is HDMI, doesn't seem to be recieving either a signal, power or both. The same goes for any USB ports, as the mouse and keyboard do not light up or respond. I have to hit the physical reset button to get the computer to boot up correctly. When that is done I lose anything that was open or wasn't saved when I powered down.

I have gone into Control Panel>Power Options>High Performance: Change Plan Settings and everything seems correct to me. The display is set to never turn off and the computer is set to never sleep since those are based on time I would rather do it manually.

Advanced Power Settings looks like this;

Additional Settings>Require a password on wakeup>Yes
Hard disk>Turn off hard disk after>Never
Wireless adapter settings>Power saving mode>Maximum Performance
Sleep>Sleep after>Never
USB settings>USB selective suspend settings>Disabled
Power buttons and lid>Power button action>Sleep
>Sleep button action>Sleep
>Start menu power button>Sleep

(It should be noted that the hibernate option seems to have disappeared from my computer. It is not in any of the options above and it not in the dropdown arrow beside the lock button on the start menu)

PCI Express>Link State Power Management>Off
Search and Indexing>Power Savings Mode>High Performance
Display>Turn off display after>Never
>Adaptive display>Off
Windows DreamScene settings>Power Saving Mode>High Performance
Multimedia settings>When sharing media>Allow the computer to sleep

In the Device Manager the keyboard and mouse are both set to be able to wake the computer.

I think that covers everything. I have been looking for a solution to this for months. Sorry this is so long, I just find that the more information I give the easier problems are to solve. Thank you in advance for any help! I hope this can be fixed!

Here are my system specs:

System Manufacturer/Model Number
Custom

OS
Vista Ultimate x64

CPU
Intel i7 965 Black Edition

Motherboard
Gigabyte GA-EX58-UD4P

Memory
6GB DDR3

Graphics Card(s)
Nvidia Geforce 295

Sound Card
Motherboard

Monitor(s) Displays
46" Samsung LCD HDTV