File Handles are automatically closed for Files on a Storage Card when a Windows Mobile Device goes to Sleep

A difficult problem to track down in Windows Mobile development is the annoying problem caused when a Windows Mobile or Pocket PC devices goes to Sleep (when it inactive for a specfied amount of time). If you have a file on the storage card open and the devices goes to sleep, then when the device wakes back up, the file handle to your open file is invalid, but your application does not know this.

Here is some more information as to why:

http://blogs.msdn.com/windowsmobile/archive/2007/01/12/everything-you-want-to-know-about-sd.aspx