The customer i am working for is still using microsoft office 2003, i think, though i really got to check if it isnt ms office 2000.
And that office has a strange quirk: if i have 2 word documents in different directories but with the same name, ms word is happy to have them open at the same time.
But the same is not true for ms excel. If i open a document Expert estmation project 1.xls from file, and i open a file with the same name from sharepoint, ms excel will refuse to open it.
No doubt there will be a valid technical reason for it, but to me as a user it looks rather inconsistent to me :-)