It looks as though your printer is over extruding filament. The filament can only go where there's space, which usually is to the perimeter/outside or up. When it's going up the nozzle goes through the goop it's producing, giving such results. Usually this is worse at the corners.
Temperature may also be an issue but I'd first get extrusion within acceptable tolerances, then see if there's any backlash (symptoms of infill lines grouped together as pairs like this: // // // // instead of regular: ///////////. One tends to over extrude to fill in the gaps between the pairs, this can be as much as 15% over extrusion. Infill not meeting perimeters on one or two sides is also an indication of backlash. Tighten belts, screws, bearings, idlers, printing plate, hot end. No lateral motion should be possible, only the intended motion.
Finally, check if the extruder is extruding smoothly ie if the extruder motor runs smoothly during longer stretches of infill. If it's moving with pauses then you should fix that too. It could be that the motor is skipping steps. You'll need to recalibrate extruder steps per mm again after you've fixed this problem.
Also note that slicer v1.2.8 and 1.2.9 has some over extrusion bugs (particularly with infill in thin walls). Use version 1.1.7 to 1.2.7 until this problem is fixed.
See:
http://forums.reprap.org/read.php?1,562959
