Yes, a warning might be a good idea. It's good that it can continue to operate, but given that that storage space is small, the user ought to be warned that they have limited time to fix the problem.

As well as a warning, it might be nice to display the track file location on the Details view (this might also be useful to people who have changed the location over time and want to know where a particular old track is stored).

It could also be useful to flag RMS tracks in the list that's displayed when loading tracks.

I'm going to load v0.5.3 in the hope that it shakes some sense into it. If not then I'll try uninstalling and reinstalling. Unfortunately that will mean I have to try and check which tracks might be lost this way (will RMS tracks be lost if I uninstall the program?). I'm hoping it's just some recent ones, but for all I know this has been an intermittent problem for a long time.

I guess the lesson for me is to maintain my tracks better. I always accept the default names, so I have no idea which ones I want to keep. Most are rubbish but I'd have to display them in Google Maps to have any idea what any of them are.