set of four melded and blue-lined then one unticked?

cinnybunz64: Hello... i was playing a game of regular gin to 10-0 and I decided to knock with an ace deadwood. One of my melds was a set of four fours. I knocked, discarded, melded my sets and hit okay. when it showed my opponents hand and mine, it showed my four of clubs unclicked... and gave my opponent the score for undercutting me. I could see no explanation for this... she did not have a run like A, 2, 3 or 5, 6, 7 clubs which would have led me to believe it was because it would have played on her hand... can you explain this at all? Another player in my league said they had experienced the same thing recently. Your advice and/or help would be greatly appreciated.