I have the same problem in the "Force Recon" mission. I also deleted the save and started over, but continue to have the same problem.
Cannot load 'C:\Users\Mutor\Documents\ArmA 2\Saved\Campaigns\pullercamp\save.ArmA2Save'.
Up until this mission I could save and reload no problem.
I'm using ArmA 2 (original DVD release) patched to 1.11.86734, no addons/modifications.
Any ideas, useful log files, other debugging tips?