This one seems to be a really famous problem for most folks in Ubuntu 9.10 Karmic Koala. So I had it too. The problem was on the initrd file. It is a kernel related file needed for booting. So i did a simple thing.
I replaced initrd.img file of my kernel version with “initrd.lz” file from the Ubuntu LiveCD and edited my grub.cfg file (equivalent of menu.lst in older Ubuntu releases), to boot using initrd.
Dropbox – the awesome online file-storage, and syncing utility finally gets a Linux client! The developers have been promising a Linux client since day one and though it took them a while to get it – it’s finally here!