i can paste any file in to external harddisk on OS el Caption

before i update os el caption every thing works fine after update i cant paste anything into my external hard disk

i have 2TB harddisk i use this to my LED 3D tv i download movies from internet into my mac n then copy into external harddisk n watch in led

i explore on net some ppl suggest that format external hardisk but i cant coz i have 1.5TB data in it.

please help me to solve this. i try to use my other 500gb external hardisk same result cant paste any thing cant drag any thing