I have a 17" iMac I bought in November of last year that is cursed with slow wireless speeds. Downloading an HD trailer off of Apple's website, side-by-side with my fianceé's Macbook results in her mac completing the download three times faster than my own. So I know it's not my cable modem or my Airport Express, because my fianceé doesn't have the slowness issue. It must be something on my computer, but what? I tried enabling interface robustness, setting the multicast rate higher, and switching the Airport Express to G-only but to no avail. Can anyone help?