Xcode stuck loading

I'm trying to use Xcode but it always gets stuck on this loading screen (attached image). I've used it before (for about an hour) and it works but I can't seem to get it to work anymore. I tried reinstalling it (I didn't uninstall, but merely re-ran the installer), but to no avail. It's always in the same place and I'm running OS X Lion on a 2.5 year old macbook. Help please.

In order to use and load the main IDE, you ave to be loading an existing
project, or creating a new one from one of the templates.

Which one of the above are doing ?

Also if your loading an old project, there might be some bad code in it, from a previous
version of Xcode.

Try creating a new project from one of the alternative project templates, and see what happens.

Regards Mark