dired problem

[Roger Mason]

Hello,

I'm trying to use dired to delete some files.  I mark them in the
dired buffer using % d and supply the regex.  The files are marked by
D.  I type 'x' and am asked to confirm deletion, which I do.  However,
the files (which have -rwxrwxrwx permissions and are owned by by
username) are not deleted.  Instead in the message buffer I see this:

(file-error Removing old name permission denied )

Can someone point out what I'm doing wrong?

Thanks,
Roger