TLDR: Don't install programs or attachments on your storage card.
I am now 100% certain that power management is behind the disappearing storage card issue, and is a culprit in a number of other bugs. It looks like when you put the device into standby, it switches off power to a number of components.
It's easy to see what happens with the storage card if you use SPB Mobile Shell. There's a handy shortcut under Tools - Browse Files - Storage Card. If you put that shortcut on your home screen and come out of standby, you'll usually see the icon return to the default unassigned shortcut. After anywhere between a fraction of and many seconds, the SD card icon will reappear.
Seems like some genius engineer at Foxconn, not knowing much about WinMo or stuff in general thought he was being very clever by saving what, 10mA? in shutting it off. Think of all those extra minutes of standby time saved.
I too suffered from a corrupted FAT, but thankfully all I really lost was MP3s I already had elsewhere. Since I figured out what's going on, I've had no trouble whatsoever. It does of course mean that I've had to make yet more compromises in the functionality of the device. The key is to
make sure not to install programs on the storage card, or if you must, make sure the phone doesn't go into standby while running them. Also,
don't choose to store email and MMS attachments on the card, or you'll get the Storage Card2 problem.
Stupid power management also explains these other things that have been bothering me, and many of you:
- Notification sounds and lights not working properly.
- Sporadic checking of email.
- Custom ringtones disappearing (Hint: put them on main memory).
- The phone randomly freezing when trying to work with Bluetooth car kits.
Presumably Sony engineers are aware of this, because if they aren't, God help us. I'm guessing that power management is such a low level issue that it's very difficult to fix with firmware if at all. That being the case, I'm not confident this phone will ever work properly and has most likely sounded the death knell for me for both Sony Ericsson and WinMo.