Vista will not fully load to log in screen Canon Multi Funct

Hi all, wonder if anyone can offer me some suggestions. For the past 2 weeks, every time I've had to reboot Vista, it would hang just before the log in screen. My Dell pc diagnostic lights one front of box were showing 1 and 2 for longer than normal during bios startup. after 30 seconds or so, they went off and Vista tried to load, but very slow So I tried changing ram cards, as lights 1 and 2 of Dell system relates to memory issue Luckily I had some ram spare from when I upgraded the ram. This made no difference to problem.I by fluke noticed that if I only had monitor plugged in, power lead and USB cable for wireless keyboard combo connected, Vista started up fine and quick. So I did a process of elimination by connecting USB cables one at a time for each boot up, all went okay until I connected the USB cable for the Canon Multi Function MP390, vista would not fully load and I got know error messages. I have installed the Vista Drivers for this device. It does work, but I have noticed even under XP, that PC lost connection to it and I had to unplug power on printer and plug it in again for PC to find it.Anyway had anything similar? Would it be the cable or the printer itself?I'm going to search and see if Canon has a Driver for that printer for 64bit version of VistaI know they released some new drivers for vista last week, but only 32bit ones.Thanks in advancePhil