in reply to Win32::OLE Open xls from http location
There are a couple of things to consider. Firstly, Sharepoint could be blocking the request for some reason. Have you tried poking it with something other than a browser (say, LWP)? It could be authentication issues, SharePoint configuration issues, you name it.
Second, it's possible something else does have that file open and lock: perhaps another copy of Excel, or a previewer of some kind.
Third, depending on your aims, you may want to consider pulling a copy of the data to your local machine before operating on it.
Ultimately, I don't think this is a Perl question so much as a general problem you're having.