Same issue, happened to me twice out of three crashsites so far. Same behaviour: reaction fire message appears, cursor moves, sound plays, clicks produce click sound, but no interaction. Can Alt+Tab and back, can Alt+F4 to exit. Happened to me with both invisible and visible aliens.
Attached save-game is right before entering the workshop where it happens. Does not happen every time I enter the building, but one of the two closest soldiers always trigger a freeze (3 out of 3 so far). Screenshot shows the position of everyone once it happens (invisible alien is where the orange squiggle is).
I looked through game folders but could not locate log files, nor do I know how to enable some sort of console in regular or debug mode. If I knew i would post log messages as well.
P. S. Maybe we all should share savegames to see if it is save-game or installation-specific.
P. P. S. Tried Resis’ save-game, same for me (replicated).
2012-02-18_10.53.29.zip
2012-02-18_10.53.29.zip