Bimal
Well it happened to me! I have been paying all my bills in time. In January my score was 720 and for the last 8 months I had been very careful(in paying all bills in time) so as to increase my credit score. I also had no inquiries in this time frame. But today as I went to TransUnion and pulled out a free credit report expecting a score close to 800, I was shocked to see that my score had acually decreased to 660.
One of three areas that they recommended I could improve on was to not go too close to the limit. Infact they also mentioned to leave a 35% cushion between the limit and the amount spent in a month.