I've been using Dropcopy for a few years now – don't need it often, but it still comes in handy on occasion. Something I've been struggling with ever since Leopard is that the dropzone disappears after a period of time, and only a restart of Dropcopy restores it. This seems to be related to Spaces, but it's hard to be certain.
I've tried tying Dropcopy to one Space, and also assigning it to All Spaces, but to no avail – it still disappears. It still seems to be running, as files sent from another machine arrive, and the progress text updates properly, but the dropzone itself isn't visible.
This has happened across machines – both my old Mac Pro and my current iMac exhibit the same behavior.
Thanks again for the great software – before the simplified sharing in 10.5 and 10.6, Dropcopy was by far the easiest way to copy files between Macs, and even with the easier sharing these days, there are times when Dropcopy is still the quickest way.