I just switched my host.
And now i am not able to see thumbnail generated when i upload an image.
Earlier i was getting this "Unable to move file to..." error.
I fixed this error by changing the permission of uploads foder to 777.
Now i can upload images but thumbnail is not generated.
I tried everything i could, chmod 777 for whole public_html
Still problem not resolved.
I contacted the host, they said contact wordpress developers.
Do i need to edit php.ini or something ?