If you aren't going to run the server kernel, you should remove it. Open System > Administration > Synaptic Package Manager. Click the 'Installed' button in the left panel and then search for 'linux-image'. Right-click the 'server' kernel and select 'remove completely' and reboot
Or you can use the terminal (Applications > Accessories > Terminal)
and enter this
At the bottom you'll see a list of kernel titles. The top title is '0'. The second is '1' etc. At the top of the page (a few lines down) is an entry 'default' with, uually a '0' after it. Change the '0' to the generic kernel number, probably '2'. Or you can just add a comment notation '#' at the beginning of the line to make it not active. Then reboot.
gksu gedit /boot/grub/menu.lst