What he says is correct.
First we have to uninstall the meego theme
The open x-terminal and run as root
If u have the cute xplorer u will find in /opt/usr/share/themes/beta a file called meegotouch and another one in /opt/usr/share/themes/plankton.
Confirm first if this files are in this directories or even another ones.
Then to remove then u cant do it from cute xplorer, thats why i said first to open x-terminal as root
To remove them type: "rm -r /opt/usr/share/themes/base" and the same for the other one and voilá now u can change themes again.
It worked for me.