This problem will appear frequently for many office2003 users in the future. You could try this Excel-VBA code (I hope you've some Excel-VBA basic knowlegde)

Public Declare Function OpenClipboard Lib "user32" (ByVal hwnd AsLong) As Long
Public Declare Function CloseClipboard Lib "user32" () As Long
Public Declare Function EmptyClipboard Lib "user32" () As Long

Sub ClearClipboard()
OpenClipboard (0&)
EmptyClipboard
CloseClipboard
End Sub

(this code is not mine, found it somewere on internet)
Regards, Kesie from Holland...