My xmegad64 based product uses xboot as serial bootloader and so far I haven't had any problems with it. But now my customer reported that the unit didn't work anymore and was just flashing one LED. After inspection I found out that there was no problem in hardware, EEPROM, FUSES nor bootloader, but the whole application area of FLASH was just empty (all 0XFF). The customer told that this happened while they were in connection with the unit through telnet and they had used the sequence to reboot the device thus entering xboot for a while before rebooting. Xboot uses AVR109 protocol, which I haven't really studied, just used with xboot + avrdude. Is it likely that the customer has accidently given an erase command through telnet (with keyboard!) or how was the program erased?
The product works just as normal now, after I programmed the FLASH again using avrdude via xboot.