5mb
I have no experience of Real Player (as I actively avoid it being on my machine but that's a different story)
Have you tried copying the files into a shared folder on your C:\ drive for example. I think your problem is just a security issue, the reason that you can have multiple logon's is so that all users can have their own private areas to store personal files.
What you could do is right click on the folder that contains the files and check that both of you have access, if not give the other access. I would still go for a shared location however.