I cannot print anymore and get the message /usr/libexec/cups/backend/usb failed", with both imac and my mac book pro

Question

Today, after printing normally, wanted tp print another page with oki ES3640a3 and epson 7900 too.
received the message that the printer stopped, and than
"client-error-not-possible"
and 
"/usr/libexec/cups/backend/usb failed"
can anyone help, I am a professional photographer and cannot miss the epson 7900.
I received the messages on my imac OSx 10.5.8
and my mac book pro OS Lion
thanks

Answer 1

Hi, did you restart the printers?
Is there a stuck job in them?
Mac OS X: About the Reset Printing System feature ...
http://support.apple.com/kb/HT1341?viewlocale=en_US
10.5/10.6/10.7 instructions...
In System Preferences>Fax & Print, Right click or Control+click on the Printers list Sidebar, choose Reset Printing System.
if you hold option and click the "-" tab it resets the printing system.
http://www.macosxhints.com/article.php?story=20031215144430486
Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions.
Any devices that previously appeared in your Printer List and Fax List will need to be added again after resetting the printing system.
Resetting the printing system in Mac OS X 10.5.x+++
To use the Reset Printing System feature in Mac OS X 10.5.x, follow these steps:
Choose System Preferences from the Apple menu.
Choose Print & Fax from the View menu.
Control-click on list of printers on the left side of the window, then choose "Reset printing system" from the contextual menu. If you don't see a list of printers, Control-click on the text "Click + to add a printer or fax" and select "Reset printing system..."
   As an alternative, if you currently have one or more printers listed, you can Option-click the "-" (Remove printer) button.
http://support.apple.com/kb/ht1341
Reboot.