Thankfully it working almost everytime .  Anyway a few days ago i found a permanent solution to this problem . So if you too are facing this problem do the following :

• Go to /etc/grub . There you will find this file called ‘grub.cfg’ .linux
• Find the line that looks something like ‘linux /boot/vmlinuz-2.6.32-21-generic root=UUID=848fb107-a42a-4755-b995-6566febd47df ro   quiet splash ‘
• Now append ‘i8042.reset’ to the end of this line .
• Now the line looks like
  ‘linux    /boot/vmlinuz-2.6.32-21-generic root=UUID=848fb107-a42a-4755-b995-6566febd47df ro   quiet splash i8042.reset ‘
• You are done

PS – This works for every version of ubuntu . You just have to find the grub.cfg or similar file if it is not there. On some versions it   is the ‘/etc/grub/menu.lst’ file.

PS – This is my first post on this blog . I didn’t know what to write so decided to start with this