There was a problem for many people after the update where it would take a very long time to load. The speculation is this was for some sort of data update process. After the game finished loading startup speeds went back to about normal. This might have been what was happening to you. Did the game just sit for a long time or did it 'crash' and exit back out to the home screen without you doing anything?

Some people report that either closing all apps (double-click home button, press and hold on an app icon that appears at the bottom and then touch the '-' sign that appears on each app) and/or power cycling the device (hold top button until a power-off switch appears on screen then toggle the switch and count to 10,20, or whatever before pressing the top button again to start the device) helps to get the app started.

Performing a backup shouldn't hurt I would think. Enable backups on your computer, connect your ipod and ensure a backup is created. On mine it does it automatically every time I connect. I think you can manually start a backup by right-clicking the device in itunes and selecting backup from the menu.

Also, Rovio is supposedly about to implement some sort of cloud save system for scores and level progress so you no longer have to worry about losing your data in the future. Bad news is it isn't here yet and you will probably need to make it through to that update before you no longer have to worry.