Failed to update Unity Web Player

When I want to play the game in my chrome browser it says:

 Failed to uptade Unity Web Player

Don't ask what game, because I've tried many unity games (in browser) and did not work. like cs-portable and even unity's stealth project game.(standalone works fine) There is also error details which says:

 A newer version of Unity Web Player is required, but the auto-update failed.
 Invalid auto-update file format.
 Please install manually.

and there is a link next to error details. when i download the installer and run it it installs very fast and says finished but the problem wont go away.

I've tried uninstalling unity web player and installing it again. same problem.

I've tried deleting unity web player related files and folders in AppData\Unity and installing it again. same problem.

I didn't do anything with my computer. I didn't install programs or chrome extension, or anything before this happen. I was playing these games like a week ago. What should i do now?

Windows 8 64-bit, latest Chrome.

//EDIT: Solved this with luck. I disabled my IDM chrome integration extension and unity updated successfully and works. I think IDM was blocking the download or something like that.