Help! Etrex 30 track memory full

[Tortoise]

I only have an hour or so to work this out, after I missed a glitch of only half a loaded file showing up on my map. New files I've loaded onto my GPS now won't 'show on map' , because the 'track memory is full'. I've checked there's still > 500mb of space available on my GPS, so that shouldn't be the issue. I'm busy deleting tracks from my GPS, but it takes ages and I'm not sure that will fix the problem.

Any quick thoughts greatly appreciated!

[Tortoise]

Never mind for now. I found that if I just 'view map' without selecting 'show on map', I don't get the error message, and I can see trace on the map. '(Normally it doesn't display without selecting 'show on map.)