I tried your VBA code and it didn't work. I'm using PPT 2003, if that makes a difference. I know very little about Macro's, but this seemed like a good time to learn. I first created a module in the VBA editor which looked like this
Sub NoFormatPaste()
ActiveWindow.Selection.TextRange.PasteSpecial DataType:=ppPasteTextSelection.PasteSpecial DataType:=ppPasteText
End Sub

I saved it. And then I copied the individual line of text from an excel document. In ppt, I clicked my newly made button (without keyboard shortcut) and nothing happened. No bug found. Simply nothing happened. Any idea what's going on here?