No longer able to store presets. Or does your V-amp sound strange, distorted and nasal? Here is how I was able to cure my V-Amp Pro.
Unscrew the lid and locate the CR2032 lithium battery on the main board inside the V-Amp. If your unit can't store your presets you want to replace this 3 Volt battery.
My V-Amp only sounded strange and nasal and all I had to do was to remove the battery, wait for proximally 30 seconds and then remount the original battery again.
Asamble the unit again and turn it on. If it still sound strange, - or even stranger like mine did you can try to reset your V-Amp to it's factory defaults. Thats how I cured mine.