my bait caster was totally fine today until later on the day when i made a cast it made a loud buzzing noise and at the same time my reel vibrated and i also got a backlash. after that first occurrence it keeps making the buzzing/vibrating and I get a backlash every cast I make. what could be the problem?

What reel do you have?

Music intro....sounds like a job for Mike (DVT).

shimano caenan

My curados sometimes make a whiny sound when they need a drop of oil on the spool brake, but they never backlash from that 

That reel has the older shimano system like the curado/chronarch e instead of the newer one with the race to oil like the curado I. I'd pop off the palming side plate and see if maybe a brake popped off the pin somehow. Check the spool tension know and make sure it isn't too loose and then if that doesn't fix it I'd send it back if it's under warranty or to mike at dvt for him to check and clean and relube it

it's nearly impossible to diagnose without seeing it. As suggested, exchange it if possible or send it in and I'll look into it. 

Just for laughs, I'd put a drop of oil in each of the two spool bearings and look at the centrifugal brake blocks and the brake drum to see if any trash has gotten in there.  You should also put a drop of oil on a Q-tip and run it around the brake drum to lightly lubricate and clean off any corrosion.  It's a quick fix that may work.

Are you sure you don't have too much line on it and some line is contacting the reel frame on the cast?  Reels don't usually "just go bad".  But lube and line are variables that can change fairly abruptly.

Obviously, I could be wrong, but I'll bet you find the problem if you carefully observe what's going on with the cast, be sure the reel is lubed properly, that nothing is loose.