Okay, my guitar (Yamaha C70) developed a fret buzz on the 1st string, 7 fret. ONLY THAT FRET, AND ONLY THAT STRING. >.<

Took it to OnStage Lajpat Nagar today, the guy increased the action from the bridge (by putting stuff under the little card thing over which the strings go, anyone know its name?). This solved it to some extent, but the action is not what I'm used to, and even after that I can still hear buzz if I play it loud.

What's the problem?
Where do I get this sorted?

Main thing, is there are luthier (experienced with CGs) in Delhi? I got an exam with the thing on Sunday!