Whenever I press "Download latest version" I always get, "Unable to save version" Can anyone help me out? its really starting to get on my nerves. Anyone who can help is greatly appreciated.

heres one of the many outputs or whatever its here:

Unable to save download. gravel4.ogg
Name: gravel4.ogg
URL: http://resources.download.minecraft.net/7b/7bf3553a4fe41a0078f4988a13d6e1ed8663ef4c
Error details: Attempting to move successful download to C:/Users\Kenneth Cripps\AppData\Roaming\.minecraft\assets\objects\7b/7bf3553a4fe41a0078f4988a13d6e1ed8663ef4c
The process cannot access the file because it is being used by another process
Filename on disk: 9e40-8bc6-be6a-fbb7
Path: C:\Users\KENNET~1\AppData\Local\Temp\9e40-8bc6-be6a-fbb7
Exists: file