USB camera question

When I connect my Canon camera to a USB port and use gtkam to download the pictures, everything works fine the first time. If I disconnect the camera, realise I haven't done all I wanted, and re-connect it, gtkam complains that it can't get exclusive use of the USB. Is there some setting I need to tweak in oder to stop this happening? Presumably unloading the relevant module (whichever that might be) and re-loading it would work, but this seems to be a bit crude. - Richard. -- Richard Kimber http://www.psr.keele.ac.uk/