Clipboard.GetData("XML Spreadsheet") return Null

Question

I have to read clipboard from a .net application using c#. I use "Xml Spreadsheet" format to read it to have informations like type of columns. My problem is that sometimes the GetData() return null.

Stream stream = Clipboard.GetData("XML Spreadsheet") as Stream;

I read clipboard from the main thread. I suppose this is a memory problem: I have this problem on some computers (32bit not on 64bit) when i put in clipboard 20000 rows.

Is it possible this is the problem? Can i try to resolve it?