"Unable to open archive" when install PRO version

We have  a free version installed in our joomla site...

When we try to intall this file "Mobile-Joomla.1.2.0.pro.zip"  this message shows in the installation processes "Unable to open archive"

What can we do?

Try to unpack zip file manually to be sure it was correctly downloaded.
As an alternative way, you can use "Install from directory" method (just copy unpacked files to joomla's tmp directory).