ulpt problem (USB_ERR_IOERROR)

Hello,

[Yesterday CURRENT/i386]

I've got some troubles with unlpt, most of the time I can't print and I
must stop cupsd, kill -9 the process usb, and unplug the USB printer.
Then it works again for some time (but mostly one time).

The printer is a Brother HL-1430 (working fine under FreeBSD since
FreeBSD 4.X)

ulpt0: <Brother Industries product 0x001a, class 0/0, rev 1.00/1.00,
addr 2> on usbus0
ulpt_attach:562: setting alternate config number: 0
ulpt0: using bi-directional mode

With hw.usb.ulpt.debug=1, I've got a lot of:

ulpt_write_callback:204: state=0x0 actlen=0 
ulpt_status_callback:328: error=USB_ERR_IOERROR
last message repeated 31 times
last message repeated 78 times
...

When it works:
ulpt_write_callback:220: state=0x0 actlen=0
ulpt_write_callback:220: state=0x1 actlen=2889
ulpt_write_callback:220: state=0x1 actlen=3023
...

Thanks in advance, regards.