I use this method when installing some old themes on my Nokia E61i and it will work on all S60v3 phones. All you have to do is set back the clock of your phone a year back or 2 years back and re-install the theme again, it will surely install.
Note:
This also work when you want to install some old applications & games, just set back the clock of the phone. And re-install the application.
I hope you enjoy your S60v3 because there are lot of bugs in it. I hope there will be S60v4 soon.......
