Your scanner almost has to be designed to share a port. Your printer doesnt have a throughput capability (both in and out for parallel). You must have the printer hooked up through the scanner which must have both in and out meaning it is designed to share. All parallel scanners are designed to share. It might not do it very well, but that is the nature of sharing devices on the parallel port.
Where did you get the cable you are using for the scanner? Does it say IEEE1284 compliant on it? Your printer needs that two way cable, and since it is going through the scanner it needs one as well.
Mustek isnt up right now, but make sure you have the latest driver for it from their site. Also get the latest driver for your printer from HP they might have improved the shared port performance with a driver update.
Where did you get the cable you are using for the scanner? Does it say IEEE1284 compliant on it? Your printer needs that two way cable, and since it is going through the scanner it needs one as well.
Mustek isnt up right now, but make sure you have the latest driver for it from their site. Also get the latest driver for your printer from HP they might have improved the shared port performance with a driver update.