Microsoft Messenger 5.0.0 file transfer: unable to receive

Most of my friends use MSN on Windows PCs. Shame ain't it. Reluctantly, but successfully, I am successfully using MSN Messenger 4.0.1 in Panther. I have upgraded to [the retitled] Microsoft Messenger 5.0.0 (for the Display Pictures functionality). This version appears not to allow file transfers to be received. The sender is told that the transfer was successful, but I am told that the sender "cancelled the transfer". Microsoft telephone support referred me to Apple & Apple referred me back to them! Nightmare!! I suspect the problem has something to to do with FTP eg enabling an FTP Proxy Server; if the latter is so, what could be the address & password?! (I am about to upgrade to Tiger: will this magically solve the problem - or make it worse??!!). Any ideas out there?! Still luvin Apple & all things Mac (except MS Messenger 5!).