key Ghosting, How can I deal with it?

This is a weird problem I came across, and though I have heard of it before, I didn't really feel it till today. In my game, I need four movement keys along with 3 other buttons for stuff like jumping and others, so I mapped the movements to the "arrow keys (Code : 37-40)" and jumping to space(32). But it seems if I press left+up+space, space won't register. At first I thought my code was wrong, but after spending a few hours on the net, I found some keyboards(and a major percentage at that) won't register certain key combinations.

So how do I deal with this situation which is outside of flash? Is there any default key config I can use and be sure it won't cause similar problems on another keyboard?

Not much you can do about it as it is outside of Flash. Try to limit your key combos into 2 keys only.