Unable to find install package

Hi there, it's me again...

I have a problem. I can't install plugins like Allvideos or Simple Image Gallery, Callendar...
Always the same problem: Unable to find install package.
In the Directory Permissions is all writable.

Any sugestion?
http://fundacionpdvictorsastre.com.mialias.net/

Please make sure that this packages don't need to unzip them first. If you can install any other extension this message tells that Joomla! installer can't find proper xml file in package which can be also related with compatibility, maybe this plugins are created for Joomla! 1.5