Downloading issue

When I try to update Minecraft and start the game, the launcher downloads a bit of files, but then crashes and displays this:
Nazwa: gd_gb.lang
URL: http://resources.download.minecraft.net/16/16e21941cf51fb5ec5ece1c33065f884b06f90d6
Szczegóły błędu: Attempting to move successful download to C:/Users\Tomasz\AppData\Roaming\.minecraft\assets\objects\16/16e21941cf51fb5ec5ece1c33065f884b06f90d6 Proces nie mo�e uzyska� dost�pu do pliku, poniewa� jest on u�ywany przez inny proces
Nazwa pliku na dysku: fcba-6911-e8c9-11bc
Ścieżka: C:\Users\Tomasz\AppData\Local\Temp\fcba-6911-e8c9-11bc
Istnieje: file
(its in polish, but basically something already "runs" (it actually doesn't) the thing.)
I tried to delete that file in the Temp folder, but the Recycle Bin says "it's already used by another process". I didn't use any mods (deleted them because they just bugged the game) so what is wrong?