Hi Sylvia.
Unfortunately I have no other printer device available for testing,
so I connected some external HDDs without problems at the same USB Port.
The only thing I observed was, printer and "old" HDD connect to port#0004/hub#0001,
whereas "new" HDD connects to port#0019/hub#0001 (at the same physical USB connector)
but I suppose this is because of USB 2.0 (printer and old HDD) and 3.0 (new HDD)
Printer is windows 7 compatible:
Kompatibilität mit Windows 7 für Canon Pixma iP4950 Inkjet Printer-Modell
Driver is also windows 7 compatible:
http://www.canon.de/images/Win_PIXMA_Full_tcm83-1073647.pdf
and I downloaded the correct drivers:
Out of the chassis? No I did not!
why that?
EDIT:
OK here's some more interesting news, I found out right now:
As I said, when I once install the printer, everthing works fine as long as I do not power off the computer.
When I reboot the system an unknown device is installed instead of the USB printing support and the printer won't work any more.
BUT...when I unplug the USB cable from the printer during boot time until windows has started and then I connect the USB cable again, the USB printing support remains active and the printer works !!!
Of course this can only be "some sort of solution" but it's very impracticable and can not be a final solution!
Elsewhere I read about some USB issues with the H87 chipsets (C1 stepping), maybe this is some similar issue here?