Well it was rock steady when suddenly i went to update the database and sentinel froze the 536 rebooted and asked for a yes or no and my computer froze. Then i discover the micro disk was screwed and suddenly on reboot of my machine, check disk had to do its thing on my hard drive. Very weird. It took me several attempts to reformat the card with sd formatter. Got everything back together and working. Tried to update again but this time just for chips and giggles i selected update firmware. Bingo!! every thing froze up again. But this time i didn't loose the SDcard. I guess i won't try updating anymore. 