Canon xt When I try to shoot sports at night under lights I am having difficulty getting my camera in maunal mode without having bulb mode as well. How do I turn bulb off? I am setting my ISO at 1600 and pushing my f-stop as low as I can go, am I doing something wrong? It worked once for a recent football game but again last night shooting soccer could not get the bulb setting to turn off.

Try using manual focus - if the autofocus won't work, because of low light, then you can't take pictures.

Follow the instructions in the "long exposure (bulb) shooting" section on page 56 of the manual available from here.

Sports mode gives you a high shutter speed. Continuous just allows the camera to keep taking pictures as long as you hold the shutter button and keep the autofocus moving.
You need very high Iso capabilities (6400+) and very fast lenses (f1.8, f2.0, f2.8) to shoot indoor sports and night games under lights and stop motion without a very powerful flash system. Standard consumer stuff just can't do it and even with a good flash it cannot work very far.
You can set the camera to night mode and it will give you your highest iso and slow shutter speeds but you will end up with motion blur.
I shoot a D300($1600) and a 70-200mm F2.8($1900) and I can just barely get away with it. To do it right cost about $8000! I'm now professionally shooting just to pay for the next camera. Hobby too Hell in a hurry.

Check your focus modes to see if you are using one that is different to usual. When a DSLR has no focus lock it won't take a picture. Also verify that the focus motor in the lens is working ok. Google 'lens focus tests' and see what you can come up with.

Light up the scene! Even pro lens would have trouble taking pictures at night. Pro shoot in highly lighted stadium with 10 000$ lens with tripod or monopod. Tamron sells entry level lens, stop searching a trick, you wont find any other than lenlighting the scene!

If you're shooting in the full Auto mode, you are not taking advantage of the capabilities of your digital SLR. Your pictures are blurry because the shutter has to stay open long enough to properly expose the picture, but the people are moving while the shutter is open. You need to increase your shutter speed or increase your ISO, which means you have to select another mode on your camera. You could invest in a "faster" lens, which means that it can allow more light into your camera, but is also more expensive. Try this excellent tutorial on using a digital SLR, then try it out with your camera (use your camera manual to find the correct mode selections, etc.)

http://www.photonhead.com/beginners/

Look at the topics under Photographic Concepts to get an understanding of the relationship between shutter speed, aperture, and film speed (ISO).

Hello parr_alp,
Please keep in mind that when shooting in low light, you will ALWAYS get some amount of blur when you are hand holding the camera unless you use a flash. The only way to increase your shutter speed is to crank up your ISO setting to 800, 1200, 1600, etc. If there is no tripod handy, brace yourself against a stationary object and remember to keep your elbows tucked down near your body when shooting (no sense in holding up your arms, too).
There is no way to increase the ISO limits of your camera while maintaining quality of your images. And once again, you will ALWAYS get a certain amount of blur when hand holding the camera. 
The external flash not firing is an entirely separate issue. This could have to do with your metering, a bad flash, bad connection in the hot shoe, what shooting mode you're in — the possibilities are numerous. The next time your flash doesn't work, write down all the settings of your camera and keep track of them (i.e. shooting mode, metering mode, flash settings, current lighting situations, etc.) You may start to notice a pattern and perhaps we can help you here.
Anyway, happy shooting, and if this response was helpful, please rate it! Thank you!
Jeff

What mode are you shooting in? If you are in almost any mode except M(anual), the camera may not be able to lock focus once you point it a relatively dark area of the sky. See if the Focus Confirmation light in the viewfinder is flashing. If it is, the shutter will not release. See page 162 in the manual for options, and page 71 for shooting Bulb exposures.

The standard canon 75-300 lens is not considered a "fast" lens. Because of this, when zooming in on objects you are actually reducing the amount of light hitting the image sensor. Fast lenses cost $$$$. Just google "Canon L Glass" and you will see what I'm talking about. Try opening the field of view (zooming out) to allow more light to be absorbed bu the image senor. Crop your subject later in whatever software you use. You can also use one of the manual modes and up your f-stop to make the camera more sensitive to low-light conditions (higher f-stop means higher film speed.. higher film speed is how fast the "film"... aka image sensor absorbs the light. for action photos, faster film speed is key!!). have fun experimenting.

you mean the flash is not opening or coming out of its enclosure? if its not opening up, its stucked! try inserting a small plastic card into the flash compartment. a hook is holding the flash from coming up like a door lock. its near the shutter button side; if its up and not flashing take a look at the bulb, if theres a change in color its dead already. dead bulb can be checked by shooting on autmode (the green mode), dead bulb will gonna shoot but flash wont go, if the flash circuitry is bad it wont shoot no matter what.