Sorry I'm late but am at the MVP Global Summit writing this from a seminar.

Below are the steps that work most commonly to recover in your situation however note that GRUB can corrupt Win7 beyond repair so if you've completed these without skipping any you might choose to go ahead and rescue your files to reinstall. Those steps are in Troubleshooting Windows 7 Failure to Start

Steps to Recovery from Win7/Ubuntu Dual Boot failure:

Boot into Windows 7 DVD System Recovery Options or Windows 7 System Repair Disk to Mark Win7 or it's 100mb System Reserved Partition (preferred if you have it) Active.

Then run Startup Repair - Run up to 3 Separate Times until Windows 7 starts and it's boot partition holds the System Active flags.

If this fails when System Reserved partition is marked Active, move the Active flag to Win7 partition itself and then try the 3 repairs again.

Be aware that sometimes GRUB can corrupt Windows 7 beyond repair when on the same HD. If problems persist I would delete it completely and then for any future Linux Dual Boots use separate HD's booted only via BIOS, or Dual Boot - Windows 7 and Linux - Windows 7 Forums.

If all else fails it may be necessary to wipe the boot sector of interfering code using Diskpart Clean Command before Clean Reinstall - Factory OEM Windows 7 which steps are same for retail.