If the SD card disappears from the phone, but works consistently in a PC, there may be an issue with your phone. Where did you buy it and what kind of warranty does it have? I'd recommend returning it for a replacement if you can. After my first 635 was lost/stolen my replacement did this. Since I had apps set to install on the SD card, in my case, apps would just disappear from my home screen, live tiles replaced by blank transparent tiles. In most cases I could turn the phone off, remove the SD card, then re-insert it, then it would work (most of the time) at least for a while.
Luckily I had purchased it from a physical Microsoft Store and could walk in and ask for a replacement. The folks at the Microsoft Store are awesome. They replaced it even though I could not recreate the problem in front of them, and the replacement does not have the problem.
06-01-2015 09:46 AM