Applications on SD Card disappear: Gingerbread bug or hardware error?

I have an Huawei Honour running 2.3.6. I have plenty of apps installed and some I have moved to a 32GB sd card. Now I notice that quite randomly some application that are stored on the sd card just disappear. (I am not talking about the apps become unavailable when mounting the USB file system on a PC, as that is to be expected.) All that remains is a placeholder-icon that will be removed once I click it, and every hint that this app was ever installed is gone. I have to go to the playstore and reinstall it. Now I wonder what the source of this problem could be. Is it Gingerbread, or a hardware error (the device itself, or the sd card)?