@hdhondt It's possible that disabling the anti-keylogger in Zone Alarm may not completely reverse the hooks and interactions inserted into keyboard processing by Zone Alarm. It all depends on just how ZA implements their anti-keylogging feature in the operating system and how (or to what extent) "disabling" it reverts those implementations back to a pre-ZA, pristine, keystroking state... and, lacking any published insight into the details of Zone Alarm's actual anti-keylogging techniques, it's impossible to know whether disabling the anti-keylogging feature completely removes any perturbations to keystroking flow introduced by ZA's installed code (disabled or not).
If the problem keeps recurring for you, you may be faced with either restarting Opera periodically whenever it recurs or else consider removing Zone Alarm entirely. The problem you describe is not normally found with Opera (or other browsers), and the only times I've seen it arise with user systems is when an anti-keylogger is present on the system or when a keyboard is malfunctioning (in which case, the problem also recurs with other software on the system).
