This should fix your problem:
- Close Design Studio
- Connect your Cricut to your computer but leave the Cricut switched off.
- On your computer select Start --> Control Panel --> Devices & Printers
- Now power on your Cricut
- A new device should appear under the Unspecified heading. It should be called USB <--> Serial
- Right click the new device and select Troubleshoot
- The troubleshooter will start and it will look for problems with your device.
- Follow the instructions the troubleshooter gives you.
- After you have finished try using your Cricut in DS again.