I have found a setting for the oleObjectFrame called ObjectIsIcon when I set this to true I get the behaviour I want for word and xsl documents that is they launch in a new window.
I have the "object change" slide initially but once I launch the files it goes aware but the Icon for word documents does not appear only the word document printed in small font in the middle of the page.
It is even worse for Excel, there is no image imbedded just the outline of a white image that if you double click will re-launch the excel document. I think there is a problem in the way your dll links the image to be used in embeded OLE objects with icons and the way it interacts with power point. Failing that you have not added the icons to your dlls resources.
Please can you investigate this.
I used your sample code for embedding OLE objects and used a word or excel document and set
oof.ObjectIsIcon = true;
oof.ObjectType = OleObjectType.MicrosoftExcel;
OleObjectFrame oof = slide.Shapes.AddOleObjectFrame(1500, 1100, iWidth,
iHeight, "Excel.Sheet.12", b);