A wubi install of Ubuntu puts Ubuntu inside windows as a program and it is not on a separate partition.
I've never used wubi but I think you can use its' bootloader (Grub) to boot it and windows.
I'm not sure what the default for an actual install of Ubuntu 11.04 is. You generally only need one partition, usually also recommended to create a second partition for swap.
Did you actually do a wubi install inside windows?
Did you have the Grub boot menu previously when booting?
Use your Ubuntu CD, boot from it and go to the Applications tab and find the terminal, open it and run this command:
sudo fdisk -l(Lower case Letter L in the command)
This should output your partition information which you should post here to get help.
I'm not familiar with Acronis so I don't know what might have happened there but I'm sure someone else will be able to help.