have a blue spot in the center of the screen it covers all the number

I would like to know if you can post an image of your screen. My phone has a setting, (although it sounds like your problem is on a much larger scale), that will leave a blue dot on the touch screen for probably a .1 of a second wherever i tap the screen, just long enough to see if i missed my target I suppose. I also have it set to leave a ghost trail whenever i am sliding across the keys, again just long enough to see why the word that appears is off by a letter. Very helpful, but it could be behind seeing if your screen were having problems, the size and duration of your spot could cover the content you've entered. Your "blue spot" caught my attention thinking it could be related. Sometimes, after an entry in a data field, if my phone hangs, i could see a similar situation. Any heat problems? Again, if it is possible to attach an image, I might see that it is similar or totally something else. Maybe anything to get a similar problem on it's way to diagnosis.

Did you hit it agianst anything? The FitBit Zip appears to have an LCD screen, and it may have been damaged by impact, leaving the blue mark at the site.