Catastrophic Error due to PivotTable Grouping??

Hello all,

I have encountered something unusual and I have no idea what to make of it. I created a frequency distribution using a pivot table and then I continued doing more work to my dashboard. I came back to the distribution table and it was totally messed up. I re-doing it by ungrouping and grouping, but it does not allow me to do either. It simply says "Cannot group that selection"... I tried opening another WS and it still doesn't work. I tried it on another work book and it worked fine. I then transferred the pivot table over to the WB i was working on and I tried saving it and it gave me this (see attached)..

I'm fairly convinced it has something to do with this frequency distribution chart, but I have no idea why. Any suggestions?