The grub that is installed with ubuntu natty narwhal is not working on my system properly.My monitor(or cpu,I don't know it properly) gives me a message that the frequency is out of range and advises me to lower the resolution.I don't see the grub menu and the monitor turns off and starts again getting me directly into ubuntu desktop.I did a new complete reinstall from maverick.Can someone please tell me how to fix this problem.Any kind of help will be