The information stored in Floating Gate (FG) memory arrays can be degraded by single, high energy, ions. Their first effect is a quick and large charge loss from programmed FGs, largely exceeding that expected based on simple models. The second phenomenon is a retention problem in hit FGs, due to defects generated by the ion. We are showing that both these classes of phenomena have peculiar erratic behavior, which can be of primary importance to assess reliability of future generation devices in radiation-harsh environments or to design error correction schemes.