I use gap4 on my mac to assemble sequences, and all of a sudden when I try to copy a selection by clicking COMMAND-C, the selection is not sent to the clipboard (although the edit tab lights up as though it has). I have never had this problem and have always been able to copy stretches of sequence by clicking and dragging to select, then choosing COMMAND-C to copy, and going into a text editor, etc., to paste. Please help!