Upon reboot after the crash, I find that I had to re-enter my log in details and cd-key, the profile I created lost including campaign progress and collectibles and I'm now stuck with the "default" profile.

yeah, i`m speaked already about that. your profile is broken as mine. you need to create new profile in game & this no crash.
and rename your savegame from default_*, to *your new name profile*_*name of misson* in

i`m disappoint too. but savegame is work....and statistics of multiplayer and rank is work fine

And where would these save games be?

savegame is there
C:\Users\*username*\Saved Games\Crysis2\SaveGames\