Dell won't wake from sleep - takes 2x to boot

I have a Dell Dimension E310 running Windows 7. I upgraded to Win7 about 5 months ago and then added a video card about 2 months ago. About the time I added the video card (NVIDIA GForce 8400 GS), my Dell stopped coming out of sleep mode. I have to hard power down and then I can restart. Only recently I've noticed that even when I shut down and let the machine sit for a few hours, it behaves the same when I push the power button as it does when I try to bring it out of sleep. Here is what happens in both cases (trying to come out of sleep or trying to start after shut down):

Power comes on to the computer (the fan starts, the lights on the box come on), however I don't hear the disk drive spin and the monitor doesn't wake up. If I hard power down and then re-power on, everything works just fine.

I have NOT upgraded my power supply and I guess the video card may be drawing more power. Could this be it? Could there be a capacitor that needs to have some charge to get things started and that is why it works on the second start, but not the first start? Or is this a bad hypothesis? Any suggestions out there?

Thanks.

 

I've now installed a higher wattage power supply (430 W to replace the old 230 W) which should be more than enough. Unfortunately, symptoms are the same: If the machine is off for a few hours, it requires two tries to startup. Any thoughts or suggestions?

 

Is there a setting in the BIOS to wake from peripherals?
Does your mobo have onboard video? If so it may not be recognizing the video card on waking.

I once had a problem similar to this (I was trying to reconfigure a video card and set it to a frequency that the monitor didn't accept). I worked through most of that by going to "the cloud" and accessing the desktop remotely from my laptop. Maybe you could do the same type of thing. You'd need to have that set up before your problem presents itself.