bandwith - 4:13 pm on Dec 28, 2011 (gmt 0)
Sounds like over-optimization to me. Was the drop in traffic sudden? Or a gradual drop over time.
Usually if you search your domain name with one of your more prominent keywords, you should be #1, along with any subpages that rank for that keyword. This immediately tells me you've been penalized due to an excessive amount of non-qualitative links like directory submissions, rather than focusing on content-rich links like blog articles.
I would suggest focusing on your content and making sure it doesn't look over-optimized - good way to tell is if it looks spammy and the keyword is everywhere you look.