I did this very clever decision to set windows 7 bootloader to ubuntu. Now I cannot boot back to windows. If I try to boot via grub it shows the windows bootloader for half a second and goes back to grub. Also the safemode of windows ceased to work, so I cannot go back and change the settings. I am totally screwed here and would not want to install the OS (both of them) again...
I have had similar issues before. the solution was to grab a Windows install CD, and to boot to it.
choose your language and press next.
click "repair your computer"
follow the on screen instructions and it will try to locate issues and repair them.
I have had similar issues when setting up dual boot, or expanding my win7 partition. good luck!