I posted a comment to an item, and forgot to include a relevant attachment.
So, I then browsed to the file and tried to post the attachment, but got the cryptic error "Data is not valid".
I conjectured that perhaps it needed me to put in a placeholder comment, so I added a comment and a comment subject (not knowing what exactly placeholders are required), and then it succeeded.
So, I suggest
#1) Fix the error to say if a comment (and/or comment subject) is required, as "Data is not valid" is pretty cryptic
#2) (Request for Enhancement) I'd like to be able to just post an attachment, without having to put in placeholder text noise
RFE: Post attachment to item without adding a new comment
Moderator: SourceGear