Strange Z lift before printing with 0.8.4

I'm a newbie user of slic3r, on a printrbot+. Using 0.8.4, when I start a print, the head lifts ~3 mm and then attempts to print. This doesn't match the homed height of the head, and seems like something that slic3r is adding.

Have others run into this, and is there a solution?

There's some discusson of this in the printrbottalk forums as well: http://www.printrbottalk.com/forum/viewtopic.php?f=19&t=840&p=7441#p7441.

Is the bottom of your model at Z = 0?

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[www.hydraraptor.blogspot.com]

nophead, this is what the file generated says - that first Z entry is looks fine to me, thought I'm not a gcode expert, but it continues to lift.

; generated by Slic3r 0.8.4 on 2012-07-04 at 22:29:57

; layer_height = 0.3
; perimeters = 2
; solid_layers = 3
; fill_density = 0.4
; nozzle_diameter = 0.5
; filament_diameter = 3
; extrusion_multiplier = 1
; perimeter_speed = 65
; infill_speed = 80
; travel_speed = 100
; scale = 1
; single wall width = 0.70mm

M104 S200 ; set temperature
G28 ; home all axes
M92 E281; calibrate E
M109 S200 ; wait for temperature to be reached
G90 ; use absolute coordinates
G21 ; set units to millimeters
G92 E0 ; reset extrusion distance
M82 ; use absolute distances for extrusion
G1 Z0.300 F6000.000

Much to my chagrin (and delight) I found the problem - I hadn't properly leveled my bed, and it was low. Problem fixed!