Starting with the changeover from V4 to V5, I started getting "Error Reading from memory address 0x00000100" every single time a program gets flashed. That is an address in the Sparkfun SVL bootloader [0x00000000..0x0000FFFF]. I don't know what is happening. I just ignore it and everything works fine after that.
I do know that you can replicate that style of error message by asking the debugger to access a peripheral that is not powered up. For example, load a program to flash and don't run it, but just leave it sitting at the first instruction in you main(). Then go to the 'Registers' window, click on 'groups', and select 'uart0'. You will see a ton of messages that the same error message about reading memory where all the memory addresses correspond to UART registers. That's because the UART is powered off at that point in main(). If your program turns the uart on at some point, the messages go away and the registers in the UART window populate with real values.
So who knows. It seems like a transient issue that got introduced with the change from V4 to V5, and it appears that you can safely ignore it.