Seems to be a common issue with 2405s. Now, Dell is great for replacements, but did you purchase it within the last 30 days? I think you are not garaunteed a new unit (you may get a refurb) after the 30 day period, but I have heard of people still getting brand-new units; the warranty is excellent. However, being that it is a common issue, you have to ask yourself if its worth it all just to get a monitor that has the same issue or even moreso. If your 2405 is very good otherwise (no or very few dead pixels, good even backlight, etc), you might end up with a replacement worse than your original. So hell, to me if the thing is perfect otherwise and you can set it to 99 brightness with no buzzing, I'd just roll with that.
Also, if you want to contact Dell, I recommend the Dell chat. I used it 3 times and everytime was great. At least if you are talking to a foreigner that is hard to understand, it is much easier to get what they are saying when it is typed (their English typing seemed fine to me, and all of them had foreign names).
