a few months ago I bought an imac 27 inch late 2013 ... ever since I have continuously problems with my external HDD that disconnect all the time and cause problems in other software (Lightroom, Adobe PS CS6) ...

a few months ago I bought an imac 27 inch late 2013 .. §16GB - and flash memory) - 3,3 Ghz Intel Core 15

ever since I have continuously problems with my external HDD that disconnect all the time and cause problems in other software (Lightroom, Adobe PS CS6) ... it is not a HDD problem, because it occurs with my 3TB WD HDD (Time Machine), my 1TB WD and 1TB IOMEGA

any one have a solution? anyone dealt with this problem in the apple care program?