Man, I'm glad to hear I'm not crazy and someone else might help me find the answer. I have the exact same problem and they just replace my springs as well. I took off the sway bar and the D bushings that you were talking about were really dry like they hadn't greased them good in the first place and was rubbing paint off. So I cleaned everything up and greased both of them up to see if that would help and the clunking is still there.I know this subject has been discussed in previous threads, but I haven't seen anything relating to my problem. Just purchased a new 2010 Titan and on the way home from the dealership with the new truck, I had to cross two small speed bumps. At only 5 mph, I had a loud clunk noise in the front end as I crossed them. At first, I thought I had hit something, but on further examination, I couldn't see anything damaged. I took it into the dealer later and demonstrated the problem to them. They had it for a couple of hours and then told me I had to have the front springs replaced. Apparently when searching my VIN in their service bulletin database, two bulletins came up. One says there is a possible problem with the front stabilizer bar mount bushings causing the noise. The other is a problem with the front springs which is the one the service technician believes is the problem. They can't tell me what the problem is with the springs ... just they need to be replaced. Wow ... a new truck and needs new springs!! Anyway they are going to do it this week, so I will let everybody know the outcome.
I had a guy that knows a lot of working on vehicles helping me and he thinks its the spring that is separating from the bottom coil bucket and making the thumping noise.
Have you heard anything else?