Unresponsive keyboard at restart during boot stage

I have an XPS 435MT (BIOS 1.1.4),  recently I have been having problems with my keyboard when a restart has been performed.

I have a dual boot arrangement, Windows 7 and Ubuntu 10.04 using GRUB boot loader.

If I power on and do a cold start, the DELL BIOS starts and the progress bar moves along fine.  The GRUB menu is displayed ok and I can navigate the GRUB boot menu with the arrow keys...this works perfectly.

But...

If I select Restart from within Windows or Ubuntu, the system restarts but when the DELL BIOS starts the progress bar seems to get stuck about half way and takes a while to complete.  After it completes the GRUB boot menu appears but the keyboard is not responsive.  I have even tried to do an F2 at a restart before GRUB menu appears and the keyboard is not responsive.   The only way I can get to select Windows to boot (on a restart) is let it select the default GRUB 1st menu option and then shutdown.  Doing a cold boot (as described above) then allows me to use the keyboard and select any GRUB boot entry.

I should note that once Windows or Ubuntu starts up the keyboard is operational, the problem is only in BIOS boot stage.

I am at a loss why this has started happening, checked my BIOS settings on a cold boot and nothing seems to have changed or be out of order.

If anyone could assist please to resolve this annoying problem I would be very grateful!

Thanks