Eu vou em frente e marque isso como resolvido. Alterar as opções de montagem de padrões para rw funcionou.
Nos arquivos de ajuda do Linux:
sync and async
How the input and output to the filesystem should be done. sync means it's done synchronously. If you look at the example fstab, you'll notice that this is the option used with the floppy. In plain English, this means that when you, for example, copy a file to the floppy, the changes are physically written to the floppy at the same time you issue the copy command.
However, if you have the async option in /etc/fstab, input and output is done asynchronously. Now when you copy a file to the floppy, the changes may be physically written to it long time after issuing the command. This isn't bad, and may sometimes be favorable, but can cause some nasty accidents: if you just remove the floppy without unmounting it first, the copied file may not physically exist on the floppy yet!
async is the default. However, it may be wise to use sync with the floppy, especially if you're used to the way it's done in Windows and have a tendency to remove floppies before unmounting them first.
A opção de montagem defaults inclui a opção async . Eu suponho que isso é o que estava causando o problema, mas ainda não tenho certeza. Se alguém souber porquê, por favor comente.