tried to update ipad, now it won't backup
I backed up my ipad onto my computer today before trying the IOS 8.4 update. I tried to do the update, and it said I didn't have enough room. So, I took some things off, and tried again. It went through the drill, then said an error occurred when backing up (no numbered error, just an error). I tried several times, then restarted my computer and the ipad. This time I went to just back up onto the computer, and the same error message occurred. Suggestions???
iPad Mini, iOS 8.3