Problem activating themes or plugins

Hi to all. I’ve searched in the posts but I haven’t find anyone that could fit my problem so I’ll explain it here

I have installed the latest version in my server, it was fine without errors or problems. I also installed the Akismeth fine but the problems start when I want to install a plugin.

I install trought the control panel in the admin area, it will install ok but when I try to activate it my page turns white. My frontend is ok but if I try to enter in te backend it’s white.

The same happens with the themes but it’s even worse because I can’t activate it, my frontend looks weird.

I also tried installing manually but with the same results. Can anyone give a clue about how I can activate plugins and themes??

Thanks in advance ^^