Problem with the first cell which contain a large string ---help

[Kiss]

HI!
i have a sheet look like:
A
1 XMLString(name of column)
2 my large string

when i use OLE to read:
dataadapter.Fill(mytable);
but there's a problem: mytable.Rows[0][0] = ""; it can't read that string.
However, when i insert the first cell is a small string and the second cell is my large string:
A
1 XMLString(name of column)
2 abc
3 my large string

then i use OLE read the large string from second cell, there is no problem happens:
mytable.Rows[0][1] = mylargestring;
I don't know why it happens that.
So i need help to read my large string from the first cell.
Please help me.
Thanks a lot.