why the yellow cast ?

The exif should be there , I'll check after I post . I had a bunch come out with the yellow cast .
Flash was a 580 II on top of shoe , flash bracket to camera broke [I got it out when I home]
I don't know what I had set wrong .

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I'll go out on a limb and say it's the white balance. I can't see your EXIF data but it might be just me.

Did you try adjusting it? From the looks of the ambient light and the WB on it I'd venture to say you should've set it up to Tungsten or Incandescent.

Also, the shot is underexposed.

I don't have much experience with flash, but I'm going to venture a guess and say that it has something to do with the lighting in the room competing with the flash. Since they are different color temps, the areas in the pic that aren't covered by the flash are going to look much different than the areas that are in the flash. However, I could very easily be wrong.

Also you used a slow shutter speed so you will get more ambient light in and as Max said you will need to adjust your wb. If you really want to get rid of that color in that type of lighting you need to boost your shutter speed.

Thanks , this is the exif data , using PS auto color [I think - didn't post the corrected picture] it came out better ,
I bracketed both WB and f stop I think .
I sized it in PS and shot in raw +jpg .

File name: IMG_2767.jpg
File size: 92749 bytes (1000x667, 1.1bpp, 22x)
EXIF Summary: 1/15s f/3.5 ISO400 28mm

Camera-Specific Properties:

Equipment Make: Canon
Camera Model: Canon EOS DIGITAL REBEL XTi
Camera Software: Adobe Photoshop CS3 Macintosh

Image-Specific Properties:

Image Orientation: Top, Left-Hand
Horizontal Resolution: 72 dpi
Vertical Resolution: 72 dpi
Image Created: 2009:01:27 17:07:40
Exposure Time: 1/15 sec
F-Number: f/3.5
Exposure Program: Aperture Priority
ISO Speed Rating: 400
Lens Aperture: f/3.5
Exposure Bias: 0 EV
Metering Mode: Partial
Flash: Flash, Compulsory
Focal Length: 28.00 mm
Color Space Information: sRGB
Image Width: 1000
Image Height: 667
Rendering: Normal
Exposure Mode: Auto
White Balance: Auto
Scene Capture Type: Standard

Other Properties:

Resolution Unit: i
Exif IFD Pointer: 222
Exif Version: 2.21
Image Generated: 2009:01:24 15:22:30
Image Digitized: 2009:01:24 15:22:30
Shutter Speed: 1/15 sec
Focal Plane Horiz Resolution: 4433 dpi
Focal Plane Vert Resolution: 4453 dpi
Focal Plane Res Unit: i

ISO 400, F/3.5, 1/15s is a lot of ambient light coming in. You were using AV so your camera was exposing for the ambient with the flash just acting as fill. Manual and P modes allow you to expose for whichever light source you want or a balance between the two. Also, those walls look yellow, was the ceiling yellow as well? If you bounce off of a yellow surface everything will come out yellow.

Get your camera into M mode. Av and Tv will attempt to get a proper exposure with the light it has not taking the flash into consideration.

Your shot is probably mostly ambient light and that orange wall isn't helping.

Go to M mode on the camera f3.5 is fine, shutter at 1/200. Let the flash earn its keep.

Titus213 wrote in post #7206121
Get your camera into M mode. Av and Tv will attempt to get a proper exposure with the light it has not taking the flash into consideration.

Your shot is probably mostly ambient light and that orange wall isn't helping.

Go to M mode on the camera f3.5 is fine, shutter at 1/200. Let the flash earn its keep.

Very Good advice...this will help you considerably.

Thanks , I'll try P next time .
Almost everything in the room was a shade of yellow .
This is after clicking the auto in PS under image . I had camera set at bracketed flash and f-stop . both were + / - 2 .
I'll reset to factory settings .

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Thanks again , I bookmarked under WB . Sorry last 2 posts came while I was posting .