Go to your profile
Then Edit Info
There is an option to use picture/change picture
Click that
You will be redirected to another page for changing your picture.
Upload any picture from your computer.
Crop that.
Then ok.
Thanks
you should give some more hints about you like your operating system,browser,etc.
Whats that flash player ? Professional or Plug-in ?
If you are using internet explorer then that may cause.
Use firefox/Safari/opera.
I think some malwares are entered into your system.