I've had the "disappearing sdcard" problem a few times now. Tried the fixes mentioned in the OP without success, so I used the occasion to do an acmeuninstall, reinstalled the jcsullins (milaq?) Android 4.2 / CM 10.1 ROM. Now I'm trying to be careful about avoiding the 50+ apps on sdcard problem.
Going to Settings/Apps/Downloaded, I see that I have 38 downloaded apps installed. Surprisingly, in the list of apps "On SD Card", I see 14 apps, most of them with 0 bytes used on the sdcard. The same apps are shown in the "Downloaded" list, but in the downloaded list, the app appears with a different size. Just for example, in the "On SD Card" list, I see "Facebook (176KB)", but on the "Downloaded" list I see "Facebook - 32.31MB". When I tap on "Facebook" in the apps list, it shows storage as follows - total 32.36MB, App 19.35MB, USB Storage app 0, Data 12.96MB, and SD Card 48.00KB. So it seems that Facebook is almost entirely stored in /data, but a very small bit of data is stored on /sdcard.
So I'm wondering ... do those 14 apps that are showing up as "On SD Card" count against that 50+ app limit? I've been looking through CM settings to find a way to direct CM to install the apps solely in /data, can't find anything.
I did run "mount | grep -c asec", which returned "1". So if that is the critical number, it appears I'm in good shape.
Just as an aside - I think the "sdcard unmounted" problem appeared after I ran Tailor in WebOS. I hadn't done anything yet in Tailor, I just got into to look at it. Another problem I noticed was that I was not able to install anything in WebOS. I tried to update some WebOS apps but every time I got an "Install Failed" message. I wonder if that could be somehow related to the "sdcard unmounted" problem I saw in CM. Another interesting thing - when i was resizing the partitions in Tailor, when i tried to check the filesystem on the "Android (data)" partition, I got a fail message, with an instruction to click a button to repair. After the first click on "repair", I got another fail message, but also a message that often two clicks on the "repair" button are needed. After the second click, the repair was apparently successful, and then I was able to do a "check filesystem" and resize the data partition. any insights on what is going on and how to fix?
thanks! especially to nevertells who is helpful even though he usually tells me to go read the whole thread.