PC cannot trnasfer files to Nexus

[laua]

Own my galaxy nexus for a few day , loaded a few apps, and transfer pictures and vedio files to it from PC. Then next day when I drag and drop a files or files to it PC open the copy widget but not action. I can see the folders on the nexus. call Samsung, they advice me to reset my nexus to factory state. I work that way. but I have to restore everything. any idea why, and any fix without a total reset.