Looking CPU usage (via ADB) I see that the gallery process takes almost all the CPU.
Connect your device with adb (I use adb over wifi) and verify that your CPU is normal.
Code:
adb connect 192.168.0.3:8000 adb shell top
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.
User 93%, System 5%, IOW 0%, IRQ 0% User 292 + Nice 0 + Sys 16 + Idle 0 + IOW 0 + IRQ 3 + SIRQ 0 = 311 PID CPU% S #THR VSS RSS PCY UID Name 5243 93% S 12 122920K 31264K fg app_209 com.littlefatfish.photo
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
adb shell ls -l /proc/5243/fd
In my case it was
/mnt/sdcard/DoveConviene_icons/segnalino_ld-market@2x.png
Now you have to remove this file (if is important for you, you should copy elsewhere).
rm /mnt/sdcard/DoveConviene_icons/segnalino_ld-market@2x.png
My gallery now it's back to normality!!!!! (at least 'till another png will block it)