Cannot upload lua scripts through mission planner, bad CRC exception

#### Issue details
When uploading LUA scripts to ardupilot, bad CRC exception error occurs. Uploaded lua scripts become all 0.
Cycling power on computer and Pixhawk 1 FC does not solve the issue. Neither does deleting and reinstalling Mission Planner.

#### Version
ArduPlane 4.3.5
Mission Planner 1.3.80

#### Platform
[ ] All
[ ] AntennaTracker
[ ] Copter
[ V ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
plane

#### Hardware type
Pixhawk 1

#### Logs

No source files, tests, logs, or entry points are identified. Start by reproducing the LUA upload failure with Mission Planner 1.3.80, ArduPlane 4.3.5, and a Pixhawk 1, then trace the upload and CRC error path. Done means identifying and fixing the cause of scripts becoming all zeros and confirming a successful upload.

Written by the indexing model from the issue text.