Umount the partition. Then edit your /etc/fstab file as root. Usually system defaults for linux partitions are read and write. Here is how to code it for defaults.
/dev/hda8 /mnt/mdk9-2home ext3 defaults 1 2
/dev/hdb5 /mnt/music ext2 defaults 1 2
These are two partitons on my two disk system, with system defaults. If system defaults do not work, add 'r/w' as an option.
If nothing works, please post the exact coding you have in your fstab file for this partition.
Hope this helps.