Basically, if I open, modify, save and close a file and then try to do anything like delete that file, I can't unless I close the Textpad application. I get error messages related to the file still being in use.
It would seem to me Textpad is failing to release something that affords it exclusive access. Or something like that.
I've just been encountering this behavior myself. I use TextPad 4.5. My scenario is this: I'm writing a program in Java using an IDE. After saving changes in the IDE, I switch to a command prompt to invoke my Ant build script. A JUnit test fails. I open the JUnit log file via TextPad and inspect it. I close the file, but I leave TextPad running. I invoke the clean task of my Ant build script, which attempts to delete the log file in question. The clean task fails. The only way to make the clean task succeed is to close TextPad. I tried your suggestion about the property, "Keep files locked while editing the text," but I've always had that unchecked. Any more suggestions?
While working in the same rhythm as I noted above, I've noticed that the locking problem does not occur if I have other files open in TextPad. With the problem more isolated and repeatable, maybe the developer(s) will have something more to say about it.