My camera has problem lately

Manual for Canon EOS Rebel XT digital camera Google Search ..you might find one from here.

If you need help to disassembly clean or repair errors or fix this camera you can download the official service manual from below link:

CANON EOS 350D / KISS DIGITAL N / REBEL XT SERVICE & REPAIR MANUAL

http://www.tradebit.com/filedetail.php/112818927-canon-eos-350d-kiss-digital-n

This sounds like dust on the sensor. You'll need to clean it. Google the words "cleaning a DSLR sensor" and you will find sites explaining the procedure with pictures and info about where you can get the supplies.

Use a separate card reader instead of the camera.

change your manual settings

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.

How I helped myself:
1. Exited WeFi installed lately
2. Went to Canon website, downloaded WIA Driver, reinstalled, restarted computer
3. Exited WeFi again (after restart)
4. And it works!

I own Rebel XT and Canon 50mm f1.8 MKII lens with plastic mount and noticed many pictures with missed focus, either front or back focusing. Meaning objects slight forward or below the intended subject is in focus. I've sent my body and the lens to Canon for evaluation and thet adjusted my focus sensors on the body. I still have problems and there are many threads related to focusing on this camera with 50mm f1.8 that the sensors on this camera do not do so well with fast lens and prone to missed focus.
Test your camera's focusing ability with a book or magazine where you focus on just one specific line and see if it is truly in focus when you review the picture.

Double check the wb settings in camera, (and be sure to check WB Shift) I'd suggest adding a Blue shift to your images to compensate for the Amber until you find something thats a decent trade off, if you can't eliminate the amber shift.