No, it doesn't match the problem at all. At no stage do I actually see an attachment called winmail.dat, although the headers (obtained using Outlook) indicate there might be one.
The symptom on the Blackberry is that there appear to be no attachments at all, but if I use the "Get Plain Text" option, suddenly they're there. Thjey're pdf files, in this particular case, not winmail.dat.
The received email looks fine in Outlook.