I had this once during a bike tour. I do not really have an explanation for it, only two ideas:
- the device got too hot (it was mounted on the steering bar)
- maybe some process was running in the background that blocked the files (indexing or file system check)
Rebooting the device did NOT help in this case, but after 1 hour everything worked well again.
The SD card (8 GB transcend ) is neither full nor broken. It is accessible through the file explorer in the X2 and works fine in my other device (Touch HD).
Will try a Scandisk SD card...
Do you have additional ideas?