keeps adding same users to list

Hi, I'm having a few problems with my Windows messenger,
the first one is that I keep getting the "someone has
added you to his/her contact list. Do you want to: Allow
this person to see when you are online and contact you...
etc." message, but they are all on my list already and it
just creates a duplicate on my list. Also, sometimes the
email address doesn't match the contact name for these
contacts, the name will be associated with the email from
a different contact on my list.

I've tried deleting all my contacts and adding them
again, I've tried reinstalling messenger, to no avail.

On a possibly related note, I can't seem to transfer
files with people I'm chatting with. This is of secondary
importance.

I would really appreciate the help if anyone can give me
ideas on how to resolve these problems.

Cheers,
Tim