Had this problem too after the upgrade to 2.1.2. First, you don't have to reset your device when the 'freeze' state occurs. Just press the back button long enough so that the taskmenu appears. Close down the photo/applications task (is not always present) and the startmenu task. Next, close the taskmenu by pressing the back button a long time. You will now enter some task (library, adobe reader etc) which is running along side. Press the home button again and your device is working again.
I found out what's causing this. It has to do with the layout setting of the photo/application file browser. If you set it to list or full list instead of large icon/thumbnail layout, the problem doesn't occur. If you then set it back to large icon/thumbnail layout it doesn't occur anymore until you shutdown/restart the device.
So the best solution is as follows: Set the app/photo file browser to list or full list layout before you shutdown the device. The first time you start the device the problem won't occur and if you want you can safely switch later to large icon/thumbnail layout without any freezes. Note, don't forget to switch to list or full list layout before shutting down or connecting the device to the PC for file transfer.
Last edited by dtanis; 03-08-2012 at 06:09 PM.