Never saw anything similar. As a first thing, I would try opening the file in a text editor (e.g., notepad) to see if it opens properly. In that case, I'd try saving with a new name and open the new file in RStudio. If it still does not work, then it may be some RStudio bug. In that case, knowing your RStudio version and session info could help.
Hello thanks for your answer. I can open this file with notepade but it write null null null .....
It is 12 ko. But the last friday when i close my file it operated...
If you get only" null null null" and no "meaningful" text when you open in NotePad then I fear you're out of luck. Your file seems to have gotten somehow corrupted/overwritten with nonsense. Unless you have an earlier copy/backup it is possible that the file's content is lost forever (hope I'm wrong...).
If your problem's been resolved, would you mind choosing a solution? (Even if that solution's just that your file is corrupt). It makes it easier for people to see which Qs still need help, etc.