The syslog message "Sep 30 16:15:40 richard-desktop photosmart_7550?serial=CN33I4116P7E: io/hpmud/musb.c 549: invalid product id string: Operation not permitted" means that the /dev/bus/usb/xxx/xxx permissions are not set correctly.
The udev 55-hpmud.rules file from 2.7.9 should fix this issue.
The syslog message "Sep 30 16:15:40 richard-desktop photosmart_ 7550?serial= CN33I4116P7E: io/hpmud/musb.c 549: invalid product id string: Operation not permitted" means that the /dev/bus/ usb/xxx/ xxx permissions are not set correctly.
The udev 55-hpmud.rules file from 2.7.9 should fix this issue.