helpless,
The symptom indicates that you're probably running an old U-Boot (perhaps 2009)? Old U-Boot does not work with kernel 3.2.xx and later. If that's true, you should restore your usb stick to the previous back up before the upgrade, and then install the latest kernel here:
http://forum.doozan.com/read.php?2,12096
Make sure you have a back up stick, too. Since your kernel is too old, and it will be a massive upgrade with this kernel when you do apt-get upgrade afterward.
After you can boot back in to Debian, consider updating U-Boot too if you want new features:
http://forum.doozan.com/read.php?3,12381.
The symptom indicates that you're probably running an old U-Boot (perhaps 2009)? Old U-Boot does not work with kernel 3.2.xx and later. If that's true, you should restore your usb stick to the previous back up before the upgrade, and then install the latest kernel here:
http://forum.doozan.com/read.php?2,12096
Make sure you have a back up stick, too. Since your kernel is too old, and it will be a massive upgrade with this kernel when you do apt-get upgrade afterward.
After you can boot back in to Debian, consider updating U-Boot too if you want new features:
http://forum.doozan.com/read.php?3,12381.