Provided your application/theme is symbian signed, if you cannot install certain themes/ games/ applications on your Nokia devices, try doing this:
When installing any themes or applications to your Nokia devices such as N95, N80, N91, N73, and N6300 etc. out of the blue you just might see this message: 'Expired certificate!' This is simply because security measures within the Series 60 operating system only let you install themes which are less than six months old. (What a Shame!!)
But all is not lost, because all you have to do is you just have to move the date on your Nokia N Series/E Series back a year, install the theme, then change the date back to normal. (Still cannot follow me? No sweat then, simply read on!). Below is a step by step instruction on how to achieve this.
To change the date on your Nokia N Series or E Series, follow these instructions:
* Click on the Menu button, highlight Tools and click the center selection key (the 'OK' key)
* Highlight Settings and click the OK key
* Highlight General and click the OK key
* Highlight Date and time and click the OK key
* Highlight the date and click the OK key
* Use the Right Navigation key to highlight the year. To change the year back one year, press the Down navigation key once.
* Press the Red 'End' key to return to standby mode.
And voila! Now install your new theme and the chance it should be installed all smooth is 99.99% (Unless you are one of those real unlucky guys who is just plain unlucky in a trillion of odds!).
If you still see the Expired certificate error, change the year back another year and try installing again. (Trust me! It also works sometimes, just trust me!!)
When it is installed successfully and you are all happy go lucky, REMEMBER to follow the instructions again, setting the year back to the present by highlighting the year and pressing the Up navigation key once (this is to ensure that you are not late by one year the next day to wherever you might be going!!)
Remember all themes have one year certificate validity so after one year you have to do this to keep using your most favorite mobile theme to be used on your cool cell phone. And you are done!