Can't wake from sleep/Hib.

I have Windows Vista on my computer and whenever I choose the option to go into sleep mode, then no matter what I do, the machine will not wake up from this mode? I have checked the motherboard leds that are showing some activity but monitor always stays asleep? When using the mouse and keyboard then also they are active. When inserting a CD in the CD drive then there are no activity at all. What should I do to fix this issue?

Even I am facing the same issue on my laptop. Therefore I had to turn off the sleep feature on my laptop completely which was under the power settings. The computer used to be on, but there was not video at all. You can even try to disable the sleep function by selecting the "High Performance" Power Option which should be set to never put the computer to sleep again. Someone said that, microsoft is working on a hotfix to solve this Vista sleep issue. Untill then you will just have to wait.

Have you tried creating a new power profile on your system? I was given a machine which used to refuse to wake up from sleep unless it was forced to turn off and then restarted again. And when I was doing so of much troubleshooting in the same profile, I eventually ended up by creating a new one and then it had worked for me. Other things that you can check is the power supply which might not be giving enough power to the graphics in your laptop, which is why the laptop is not able to resume from sleep mode.