Excel error when inserting a row

[David]

when i try to insert a row in the middle of a worksheet
excel gives me an error message: "to prevent possible
loss of data, Microsoft Excel cannot shift nonblank cells
off the worksheet. try to locate the last nonblank cell
by pressing CTRL+END, and delete or clear all in cells
between the last cell and the end of your data."
I used to insert a row in middle of my worksheet without
any problems. could some one please tell me how to fix
this problem?

Thanks,
David