I am running Studio 6.1 on Win8.1 on two different PCs. One is working fine (with McAffe), the other (with Norton 360) cannot find any programmer and not even the simulator. The installed AVRISPMk2 is shown correctly in the Windows system manager and works fine on the second PC.
I found a description for this problem in Atmel Studio 6.1 Release Notes under FAQ point 8. One should search avrdbg.exe and make an exception in Norton.
I can only find avrdbg.dll, but no avrdbg.exe.
An exception in Norton of this DLL and / or the complete Atmel Studio 6.1 does not help.
Also tried a complete new installation with USB, Jungo, Atmelstudio and the necessary Visual Studio after correct uninstallation. No result, no programmer.