The first of three, good, half-hour videos all about the Canon AF system can be found here: https://vimeo.com/36931479
It is far, far more likely that you've set something wrong or are using the camera incorrectly, than there's an actual fault with the camrea or lens. Getting frustrated and just wildly trying different settings may make things worse.
Watch that video and refer to the camera user manual.
Flashing BUSY all the time may indicate an issue with the memory card.... It also may be that the AF is struggling to lock onto something in too low light (or set up wrong). The camera is probably set to prevent shutter release if focus hasn't been achieved. That will likely cause the AF points to flash red. Or, it might be that the light is so low that it's not enough for an exposure, in which case the readout in the viewfinder will flash a warning.
There are guide books available, too, that expand upon what's in the manual and can be quite helpful when learning to use a new camera. I always make a point of getting at least one of those guides whenever I get a new camera, to learn to use it well as quickly and easily as possible. I've bought and can recommend books by David Busch, Charlotte Lowrie and Michael Guncheon, but there are likely some others that are excellent too (check the feedback on Amazon).
Sure. It is possible something is wrong with the camera... but is really far more lilkely that it's something simple set up incorrectly or not being used properly, that's causing the problem.
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER
