I have a 2GB Express. I record from FM, approximately 10 minutes at a time, and usually cancel. (I’m waiting to record something specific, and if I don’t hear it then I cancel the recording.) After I do this a few times, I get “No Memory”, even if I haven’t saved any recordings. When I connect to the computer and select “internal memory” and then “Properties” it shows 1.9GB used. When I double-click on “internal memory” to see the list of folders, and select all the folders and click “properties”, it shows 1.2GB used (which is approximately the size of my music files". So it seems that when I cancel the recording the file isn’t saved but the memory isn’t released; either the file remains but is hidden, or there’s a problem in the directory.
There’s a temporary solution; if I shut down by using the reset procedure (select button and vol+ button) I get the memory back.
I updated to the latest firmware, and this didn’t solve the problem. On the bright side, with the new firmware the Express no longer shuts down when I select “Back to music list”.