Problem updating database

[Obsidiandream]

I get a window that says "Only 1 instance of this program can be running". and I get this error message.

1.1.1 Unknown Thread Error: mscorlib
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access)
at EQ2MAPUpdater.MainWindow.GetFileMD5(String strFilePath)
at EQ2MAPUpdater.MainWindow.DownloadUpdates()
at EQ2MAPUpdater.MainWindow.GetUpdates()
at EQ2MAPUpdater.MainWindow.Timer3_Tick(Object sender, EventArgs e)
at System.Windows.Forms.Timer.OnTick(EventArgs e)
at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)The process cannot access the file 'C:\Sony\EverQuest II\UI\eq2maps\par\images\maps\map_exile_city.dds' because it is being used by another process.

I'm slightly confused, sorry if I am making a dumb mistake.