Thank you for all of your prompt and polite responses.
The problem was - I had ringtones that were longer than 40 seconds.
After searching a bit, quite a lot actually, it seemed like this was the likely problem. I do not know why, but making them all less than 40 seconds seems to have worked.
I started from scratch, used iTunes (Control click, Get Info, Options, set start and stop) to make them less than 40 seconds. Converted to ACC. Copy to desktop. Delete old from iTunes. change from m4a to m4r, copy back to iTunes and they all showed up in Ringtones and were synced with my 3G.
