Need Help With Printing Problem

All of a sudden I have a problem with printing photos. When I print a 4x6 photo, there is a 1/4" white border on each end of the length of the picture. The top and bottom are borderless which is what I want. Everything appears to be set correctly in the print set up, 4x6 paper selected and landscape selected. On DPP, even though no trimming was done to the photo, the aspect ratio is set to 3/4 which I believe is correct for this size print. Anyone have any answers? Never had this problem before but the photos were taken with my wifes point and shoot Canon SD790 IS and not my 40D. I wouldn't think that should make any difference at all. Thanks very much.

It's to do with image ratio's.

Your 40D has an image ratio of 3:2 so it fits in perfectly with a 6 x 4 print.

The SD790 has an image ratio of 4:3 which means if you are trying to print this uncropped as a 6 x 4 you will be left with blank bits to the left and right edges as scaling the image up it will actually be 5.33 x 4 inches in size.

The correct ratio for a 4" x 6" is 2:3 , not 3:4.

Thanks guys, I will check this out.