Hey,
I'm familiar with this problem. Everytime I am logged on and try to upload something after I downloaded something I get this error message in the progress bar of the upload. To upload something I need to refresh the page. This will bring me to the sign in page or even the public home page of asuswebstorage.com. Then I sign in again, go to the right folder, where I upload the document.
This same problem with signing in if I want to do something on the drive is when I want to download a document. Everytime I want to download a document I need to sign in again. Even if the time between two downloads is only a couple of seconds. This is very frustrating, costs time and doesn't make the uses of the storage as good as Asus says.
I already tried to use another browser, but after using IE, FF and Chrome and different versions of them all, it didn't help.
I hope you can help me with this problem.