When I insert a certain Maxwell DVD+RW disk (nearly new and a disk I've successfully used several times before) into my Panasonic DMR-ES15 DVD recorder I get the message "This disk is not formatted properly. Do you want to format the disk in DVD Management?" So, I check "yes and yes and start", the formatting seems to proceed normally and about a minute later I get the message "Formatting complete". However, if I try to record on the disk I still get the message "This disk is not formatted properly." Could I have inadvertently done something to this disk in my recorder that now makes it unusable?