Since Mavericks my HP Scanjet 2400 doesn't work anymore.

Hello sama,

It sounds like you are not able to scan after upgrading to OS X Mavericks. I recommend following these steps to troubleshoot the issue you are experiencing:

Follow these steps until the issue is addressed:

1. Make sure that the printer is powered on, has ink / toner, and that there are no alerts on the printer’s control panel. Note: If you cannot clear an alert on the printer's control panel, stop here and check the printer's documentation or contact the manufacturer for support.
2. Ensure the printer is properly connected to a USB port on the Mac or AirPort base station / Time Capsule. If the printer is a network-capable printer, make sure that it is properly connected to your home network.
3. Use Software Update to find and install the latest available updates. If an update is installed, see if the issue persists.
4. Open the Print & Scan pane or Print & Fax (Snow Leopard) pane in System Preferences.
5. Delete the affected printer, then add the printer again.

If the issue persists, try these additional steps:

1. Reset the printing system, then add the printer again.
2. If the issue still persists, reset the printing system again. Download and install your printer's drivers. Then, add the printer again.
3. Contact the printer vendor or visit their website for further assistance.

You can find the full article here:

Troubleshooting printer issues in OS X

http://support.apple.com/kb/ts3147

Thank you for using Apple Support Communities.

Best,

Sheila M.