Hi, I use iphotoplus to scan photos and usually have had no problems.
I use 100 dpi setting, and (unless I want colour) use the grey setting. I find the line one seems to lose too much on black and whites. I save the file as a .jpg which gives it a manageable size (the b/w doesn't seem to allow it to be saved as a .jpg). The photo of me on BBC is a colour jpg file scanned in the above way.
Trust this helps but then simple operations never seem to be in computer land.
Rana