I have been optimizing for a very competitive keyword for about 6 months. I've done a lot of optimizing - I have PR8, PR7, and hundreds of PR6 backlinks. My on page optimization is really good, and I've tried to take a slow, controlled ride up the SERPs. For the last 6 weeks, I've been stuck at 32 or 33 in the SERPs, and no matter what I do it doesn't change. Its like I've hit a ceiling. The ceiling should be when I'm at #1 for the keyword, but instead I've been locked in the lower 30's for weeks. I don't even really know much about the -30 penalty, but I seem to be sitting about 30 spots below where I should be. I was increasing my SERP by 5-7 places per week, and if I'd stayed at that rate, I would be in the top 5 right now. Am I being penalized in some way?
I don't know the nature of your site nor the keywords you are trying to rank for. In any case, i have experienced that same thing but it lasted only two (almost three) weeks and than suddenly I found myself on the 3rd page of the SERPs. I don't know how I could define this actually, but what I could advice you (what I did) is to continue do the same thing you have done till now. In my advantage it was the fact that I was waiting like 3-5 days for every minimal change I would do in the on page optimization and 2-3 days on the off page optimization (which did helped me a lot to find out things that worked and things that didn't worked). What i could say is, i doubt you are being penalized unless you started massively building links (and from what I have read from you here on DP i doubt you would do such a dumb move). Just give it some more time, build a backlink every 2-3 days and wait, monitor and see what happens (I know, patience is not something we really have when we want to see our site in the first page of the serps).