Bugs in Excel cells

I have been working in the summer. The VBA programs that I have created do help me to merge the data. The only problem is that the data is too large and sometimes Excel becomes too busy and does not respond.

There is another problem which is unrelated to be program. No other characters can exists in each cells inclusive of those hidden unseen characters. There are millions of cells in Excel.

I am encountering this problem at row no. 5762. There are another 1000 plus rows beneath that needs to be checked and merged ! So I will take some considerable time.