IWMReaderAdvanced4::CanSaveFileAs weird behavior question?

I really not sure this is the right place for the following question:

I'm experiencing very strange behavior of IWMReaderAdvanced4::CanSaveFileAs.

It constantly returns not predictable and sequentially different results for the same remote content from the same web server. Would love to know: what influences that Is this behavior by design Maybe current server load influences returned value Or maybe something extra should be done on the client before the call to it.

My app uses the same sequence as described by MSFT in here:

http://msdn2.microsoft.com/en-us/library/aa390697.aspx

Regards,

I