This is a year later, but maybe somebody finds their way here and encounters the "Test connection failed because of an error in initializing provider. Invalid UDL file." or similar UDL error. I got this and investigated other how-to-define-SSIS-Excel articles. This one

http://blog.tylerholmes.com/2007/12/walkthrough-connecting-to-excel-2007.html

mentioned that you must install "Microsoft Office 12.0 Access Database Engine OLE DB Provider" and gave this MS link:

http://www.microsoft.com/downloads/details.aspx?FamilyID=7554F536-8C28-4598-9B72-EF94E038C891&displaylang=en

When I install the MS component and follow the steps in the first link -- they are slightly different from this SQLServerCentral article -- the UDL errors go away.

If an additional download is indeed the fix, then that sucks -- MS gives us the option of picking a Connection Manager OLE DB Provider that is not loaded on the system...ugh.