This tends to happen with the market from time to time. This is the 4th time I have personally seen it happen since I got my MotoDroid in February. Just give it a couple hours and then try again.
Usually what is happening is Google is making updates to the market or their servers. typically this doesn't last more than a couple hours, but I remember one time last April (May maybe) where it lasted just shy of 24 hours.
The other thing that could be happening is a technical issue on the server side. Google is a high profile company that a lot of very sinister people look to as an "easy" target for trying to steal info or simply block traffic (DoS or DDoS anyone?)
Seeing as the market is loading just fine and there are no other issues with any of Google's other services, I would say that this is an isolated issue with the market; specifically concerning downloading apps. That said, I know that Google just recently implemented market searches into their mobile search widget. They may be optimizing the server for better search performances with this new update.
Also, I have heard rumors that Google is (or at least was) going to upgrade the market to allow for desktop searching and, ultimately, pushing apps to your phone. If they are actually working on this feature, then they may be optimizing the server to better handle such a feature.
There really are too many things that could be happening to be able to pinpoint the actual cause of this without having full access to Google's servers.
One more thing. Since there are so many people on this forum experiencing the same issue, then I would say that everyone is having this problem. This means that it is not a carrier or phone specific issue.
Again, just give it time. It will be up and running properly again soon.
Kratos
