Running/jumping problem

In my first platform game I have problems with movements, apparently I cannot jump when I'm pressing left/right button and jump button simoultaneously. Anyone know what the reason may be? Thank you in advance

Are you using the default controls? if youre not, post an image or something of your events, to lets us see and locate your problem ^^

http://postimg.org/image/4qyk8nny9/

Change keyboard event "space is down", replace it with "on space pressed" and try

I've tried it, but it didn't work.