Hi,
The problem I faced was a lack of permissions even if it didn't say it (I simply got no response from clicking "enter license key"). So, after opening a terminal and as a root user I ran:
/usr/lib/vmware/bin/vmware-enter-serial
Then I was able to finally introduce the serial key 
I guess that running workstation 9 as a root or "sudoing" will also make the same effect but now thats working...I won't touch it LOL
Regards,
elgreco81