Connect your device with adb (I use adb over wifi) and verify that your CPU is normal.
The "top" command prints cpu usage every 5 seconds or so.
Scroll up and take a look at the first line.
You should read low values for User and System % (mine is "User 0%, System 5%")
Start gallery on your device, now you should see the cpu usage very high, say over 90% for user.
The first process listed is the one hogging your cpu.
The name of the process could vary (say com.cooliris.media).
Write down the PID (in this case 5243).
Hit CTRL+C, adb exit.
Launch adb and take a look at the files held by this process, issuing
In the list you should see only one media file, the one that is blocking the gallery!!!
In my case it was
Now you have to remove this file (if is important for you, you should copy elsewhere).
My gallery now it's back to normality!!!!! (at least 'till another png will block it)