I have Avast on four computers and access Wuala from all of them. On one I updated the Avast Software to the 2014 version 9.0.1501. I got the same problem with Wuala as mentioned in previous comments.

Wuala can not help. I found the solution in installing an old version of the Avast, the 7.0.1474 software version.
Now it works again. Since I do not use all the bells and whistles of the Avast software it suits me just fine. The menue is also a little easier to use. In the setup section I set the program update to MANUAL so that I am not constantly reminded to install the new software.

This experience with Avast makes me look around for another software. This especially since I have another problem with Avast when trying to run the Amateur Radio software Echolink.

Good luck to all of you (BTW: it reminds me of Norton. They did not listen to the user!!)
Ueli Hauser