Adding a file to SharePoint can be implemented through a web service as described in the
note from Microsoft. It works fine - for all types of documents except for Office 2007 documents!
Upload goes fine - but when you try to open the file using Office you get the following errors:
The Office Open XML file cannot be opened because there are problems with the content.
Solution
SharePoint seems to have an error when adding documents to the filecollecting using the
SPFolder.Files.Add
function. If you add from a byte-array it simply fails with Office 2007 documents. But if you convert the byte-array into a stream, e.g. by saving the byte-array into a file and loading it into a stream, then it works. It's unclear to me why this error occurs - but Microsoft probably drops a single byte in the byte-scenario - which is critical for Office 2007 documents, but other documents seems to survive.
Input and comments very much appreciated.