Comment 14 for bug 118283

You can make your fat filesystem permissions look like matching to your default umask.

Mount options:

for umask 002: dmask=002,fmask=113
for umask 022: dmask=022,fmask=133

(do not use the unspecific umask option)

As a workaround adjust your personal hal vfat mount options in the gconf-editor, but the defaults need to dealt with by ubuntu.