Vertical Line Bleeding When Scanning With Image Capture to PDF

Lately I've been having trouble scanning documents with any of my Macs and my Brother 7820N printer. The printer is connected directly to the Mac via USB and I'm scanning using Image Capture (I'm no longer using the Brother Control Center utility as it has become too unstable since Leopard). The issue I'm having is that when I scan my documents and save them to PDF format, the scan will almost always "bleed" when it encounters solid lines. For example, if there is a signature line on a document, it seems "bleed" on that line and everything on the rest of the page looks like a bar code. All text pages come out fine. If I switch the order of pages, the same thing happens. I've tried scanning on all settings and it happens each time to different degrees depending on the resolution. Interesting, in the preview window the scan looks fine. That tells me that something is happening when it converts the image to PDF (using Preview but same happens using Acrobat). I can scan the pages to TIFF files and convert them to PDF but that's time consuming. The benefit of scanning to PDF is that I can scan multiple pages into a single file which is important for my work.

Has anyone else experienced this problem and discovered a solution or work around? Scanning to other formats works but significantly increases the time it takes to create a multi-page PDF. I really don't think it's a scanner problem since the preview images are fine. It has to be something in the conversion to PDF.

Thanks