so, the problem(gdb complain memory access error) only happens when you open a file in a different folder(not the project folder)?
That's right - if I open the data file while it's in the project folder I don't have a problem. It's only when I have to navigate to a different folder (using the file dialog) that the problem appears.
Well, it gets stranger and stranger. This morning I created a new project (with a different project name) in the same folder as the files for the test case. I went through the wizard, created a blank wxwidgets project, then added the .cpp files from the other project once it was created. The problem with single-stepping was not present. OK, so it's something to do with the project settings I thought to myself. So I went and rebuilt the project as included in the zip test case.
The problem had disappeared there too! OK, so maybe there are some files that are being updated from one project that affect the other. I did a 'clean' and verified that all object files and executables were removed (or I deleted them myself). I also checked the dates of all the files in the main project folder. The only files newer than the zip file I posted were for the newly created project (a .cbp and .depend), and a .layout file for the original project. I opened the .layout file in an editor and could not see anything in there that would affect anything (it was only a couple of lines long). I rebuilt again and tried the debugger - it's now working (this is the tdw version) as it should.
OK, so all I need to do is create a new project for my original (full) project, which I did. The Single Step Problem is Still There... :?
The Full Moon is only 4 days away, maybe that's it.