Few Suggestions, Questions.
Have you just carried out an upgrade in software?
What colour is the USB cable your using?Suggestion to try the following:-
Could you navigate to the 'device manager'. Normally this can be achieved by 'Right Clicking' on ''My Computer'' and clicking on ''Manage''.
On the left hand side you will see there are 6 options in a box, the last should be 'device manager', please click on this.
Now in the center of the screen you will see a list of all the hardware features of the PC/Laptop you are using.
Depending on your operating system and how new the scope is you may have a section called 'Pico Technology Instruments' otherwise the driver for the scope can be found in 'Universal Seriel Bus Controllers'.
It maybe the device is showing as a 'Unknown device' which you can confirm by unplugging and re-plugging it in and it will reappear. Otherwise it will be shown as the following 'PicoScope 4000 series PC oscilloscope'.
If you right click on the driver and select 'Uninstall'. You will be asked to confirm the uninstall, there is also a check box for 'delete driver software', please select and enable this, then confirm by clicking 'OK'.
Then simply unplug the scope from the USB port and re-connect, then allow windows to find the driver and reinstall the device. You should be prompted by a message saying the device was successfully installed.
Then restart the software and the scope and software should operate normally for you. You may need to plug the scope in on all USB ports as some operating systems wont install the driver automtically i.e. Windows 7 will.
Let me know how you get on
Lee - Automotive Technical Specialist