Re: bowlback buzzing - whats up with my baby?
If the instrument buzzes at a particular frequency and not only in some particular location, then I'm afraid that the problem is probably not just a bum string; perhaps something (e.g. a brace) is loose inside the instrument. Before opting for surgery, however, please check out EVERY other possibility: things often go abuzz by the nut (string ends against other parts of the headstock), or down by the tailpiece (ditto, although less likely). If the buzz persists, a look inside the bowl (with a hanging flashlight-bulb and an articulated, "plumber's" mirror) might reveal the problem. Ultimately, you may need the services of a qualified repairman.
Best of luck, my friend!
P.S. To be more optimistic: there are also those "fluke buzzes" that appear out of nowhere, and vanish back into nowhere within a day-or-so. Weather, humidity, and the rest... Do not take any action until that "fluke span" time expires.
It is not man who lives, but his work. (Ioannis Kapodistrias)