Hi Ignaciao,
Here is an update... I deleted the app from my phone and reinstalled from the AppStore on the phone (not through iTunes on the computer) - this time with more than 2.5 GB free.
The app had no problem installing and now launches just fine.
I am guessing that the low amount of free disk space when I originally installed was the problem.
Perhaps now you can test with a nearly full iPod (I think I had just 75MB free) and see if you can replicate the problem.
Hope this helps.
Thanks for your assistance.