Don't blame things you don't know
Don't blame "browser plug-ins" unless you know it is actually a cause of Browser Plug-ins. I am using opera with no plug-ins at all (opera doesn't allow custom made plug-ins as it simply doesn't need them) and the "sticky keys" issue is occurring here. As Opera is the most standard compatible browser I would suggest the problem more likely sits within your own coding and not a fault of the browsers. I don't after all have issues with many man other flash games.