Grub is not displaying in ubuntu 11.10

I've recently installed ubuntu11.10 in my pc. I was working with windows 7 already. After installing ubuntu 11.10 the grub is not displaying when pc starts. instead, the monitor is saying that,
"The current input timing is not supported by the monitor display. Please change your input timing to 1600x900@60Hz or any other monitor listed timing as per the monitor specifications."
After the message is shown, the system goes to ubuntu login screen and later I can work as usual. I can even select the windows 7 OS by pressing the down arrow in my keyboard even though the message is displaying. So, i hope the grub is working normally. During shutting down in ubuntu 11.10, the same message is displaying instead of ubuntu logo. The issue is not seen while using windows. I think there is no issues with the monitor as I had used it with ubuntu 11.04.
My monitor is 'Dell IN2030M'. I'm using AMD sempron(tm) 145 processor.
Please help me to solve the issue.