Installed Lightroom 4 but cannot get it to print with my HP Photosmart 8750 printer. All drivers confirmed correct for Windows 7 by HP diagnostic software. On clicking Print the HP printer comes to life as though it is about to load the paper, it then pauses for about a minute before switching to standby. The file to be printed shows up in the Print Manager as though it is printing. When printer returns to stanby the file is removed from the print manager as though it has been printed. Printer works fine with all other packaged including Elements 10. Spent two hours on line last night with Adobe support assistant but he was unable to sort the problem. Any ideas?