Very nice piece of software you have created!
Copying text and images from Windows works fine for me. Copy text or images from a Mac (Snow Leopard) does not work. On the Mac I can paste the text and images copied to the clipboard from a Windows machine, but the Mac will not copy to the clipboard. I have full read/write permission to the clip.txt file on both machines. On the Mac I can open clip.txt and manually type text in and then save it. The Windows machine will then paste that text. If I try to copy using the hotkey or system menu in the Mac then nothing is copied. I haven't tested in Linux yet.