I don't know, but that's a pretty serious problem. The ! indicates that the file was changed outside of 4coder but it is not 100% reliable.
I will need more information. If you're not comfortable sharing some of this here you can send it to [email protected]
1. What OS?
2. What source control are you using?
3. Are any of these files on a shared/networked drive?
I will have more followups depending on your answers to these.
P.S. this is a pretty serious issue. As long as it remains unresolved things like "save all buffers" commands will fail. So I recommend returning to 4.0.20 as your main editor if you start having any issues.