Header Font Problems

Hi Guys,

I have recently adopted a wordpress site for my new company. I have been editing it and have hit a wall. My header fonts were working fine until the other day and now they are all being displayed in serif font (times) when they should be displayed in Sans Serif. I have been through the CSS and changed all the font families I could find to Sans Serif but the problem still exists.

Any ideas?

Thanks,
Ben