printing with hp deskjet 845c

[starlord]

i have some problems getting hp to work with cups(14,15).
first if i try to print web page from mozilla it does this:
-initializes printer
-goes error mode
-i'm pressing button to flush the printer buffer
-there's message from cups on the paper saying unable to open device,quitting.

when i do cat Hello > /dev/usb/lp0 it does:
-init printer
-print hello
-goes error mode
-flush printer buffer

it does print it right but it shouldn't go error mode


anyone have a solution for this,i have been searching for post but nothing seem to help me.