Message "Exception: Incorrect padding"

Hi

 

I've just configured a new policy security. I go to open the url and give me this messesage "Exception: Incorrect padding". Do you know this error?

 

The url has this img, por example: with the img=

 

I don't know the "why" the this message, can you help me, please???

 

Let me know if you need more info.

 

Thanks a lot