I've had this problem ever since I got my Focus last year (Nov - Dec). No matter what size the file is, any email attachment takes AT LEAST 5 minutes to download. I tried sending a 2 KB file to my phone and it took 6-7 minutes to finally finish downloading. With anything bigger than 10 KB, I have to start the download, put my phone away, and come back to it much later in the day for it to finally be downloaded.
It doesn't matter if I'm on 3G or Wi-Fi, both take forever.
Does anyone else have this issue or know how to fix it?