I may have unmounted something by mistake

I was having a look at Disk Quotas, which directed me to Disk and Network Filesystems where I attempted to enable quotas. As /(root filesystem) was not a link I may have clicked on some of the 'Yes' links in the In Use? column.

Now, whenever I try to navigate in Webmin I get 'Failed to open /etc/webmin/apache/site for writing : Read-only file system' and my websites are down.

It seems as though I have unmounted something, any idea what I need to do to get back to normal?

Would a reboot resolve this, I'm hesitant to try in case I make things worse.