Blue square icon in one of my files

OP, try these steps.

- Open the "corrupted" file in the PSPad hex editor.
- At the very beginning of the file, remove any characters with a hex value of 00 (two zeros).
- Save file.
- Reopen file in PSPad text editor. Do you see text?

When PSPad sees a character with value zero, it might think that's the end of the file. Remove those "null" characters and you might be able to see the rest of the file after the nulls.