Error: checksum mismatch, Last Line:0 Resend:1

Hi,
the 3D printer RepRap Prusa Mendel was working nicely.
However upon boot up today, the extruder temperature went up to 280 degrees celsius, rather than 220 degrees celsius.
the 3D printer then calibrated itself on 1st start up and tried moving z-axis (that is, from front to back) and heat bed was back to the maximum and tried to move further back for about 10 seconds.

I have rebooted the computer and same error occurs.
Full error output is:
Error: checksum mismatch, Last Line:0
Resend:1
Serial Error: Line Number is not Last Line Number+1, Last Line:0
Resend:1
Error: checksum mismatch, Last Line:0
Resend:1
Error: checksum mismatch, Last Line:0
Resend:1
Error: checksum mismatch, Last Line:0
Resend:1
Error: checksum mismatch, Last Line:0
Resend:1
Error: checksum mismatch, Last Line:0
Resend:1

Also, when I Check temp, the output is also unusual with the output: SENDING:M105.

When this happens, for me it helps really well to turn off the entire printer, disconnect USB, reconnect it and start up the machine again. After that, start the software again and see if it goes away. Usually for me it works after restarting the printer.

I think for me the problem has to do with a cheap and crappy USB hub.

You did not mention which firmware and electronics combination you are using.

280 Deg. C can damage you hot end insulator if it is PEEK.

Thanks. For the record, started working again after a couple of days and unplugging the USB and PSU.

Here are some settings from the gcode:

; generated by Slic3r 0.9.8-dev on 2013-06-19 at 17:36:53

; layer_height = 0.4
; perimeters = 3
; top_solid_layers = 3
; bottom_solid_layers = 3
; fill_density = 0.4
; perimeter_speed = 30
; infill_speed = 60
; travel_speed = 230
; scale = 1
; nozzle_diameter = 0.4
; filament_diameter = 3
; extrusion_multiplier = 1
; perimeters extrusion width = 0.42mm
; infill extrusion width = 0.42mm
; first layer extrusion width = 0.42mm

M104 S210 ; set temperature
G28 ; home all axes
M92 E660 ; set for pink - kmf
M109 S210 ; wait for temperature to be reached
G90 ; use absolute coordinates
G21 ; set units to millimeters
G92 E0
M82 ; use absolute distances for extrusion
M106 S99
G90 ; use absolute coordinates
G21 ; set units to millimeters
G92 E0
M82 ; use absolute distances for extrusion
G1 F1800.000 E-1.00000
G92 E0
G1 Z0.400 F13800.000
G1 X118.763 Y124.246
G1 F1800.000 E1.00000
G1 X117.533 Y126.366 F540.000 E1.05766
G1 X117.053 Y127.096 E1.07821
G1 X116.873 Y127.326 E1.08508
G1 X114.843 Y129.576 E1.15637
G1 X114.423 Y129.976 E1.17001
G1 X114.203 Y130.156 E1.17670

This might be a double post, please go to and use [forums.reprap.org] instead.