I just bought LR4, and everything works perfectly (though a bit slower than LR3), except when I try to go into the map or web modules. Both hang the application with 'not responding'. This 64 bit version on Windows 7 pro SP1.. help please! I had no previous issues with LR3 64bit. In fact, the map module in the beta was fine as well (I didnt try the web module).
I have the same problem on Mac OS X. It doesn't require a secondary screen - just right-clicking on a folder or selecting a collection can trigger it: It consumes an entire CPU and is no longer responsive.
The same is happening with me and the nice support people at Adobe took control of my computer yesterday and couldn't get it to work either. They promised to call back, so they must be working on it still. Hopefully soon as i have three customers awaiting their online proofs. Will try out the web upload function in Bridge in the meantime.
Adobe sent me a link to Lightroom 4.1. I simply installed the upgrade and the Web Module worked perfectly. HOWEVER, the next time i opened up the program, uploaded hundreds of business headshot photos from eight people, created Collections for each one, and then went to upload their proofs, it got hung up on Export Identity Plate' again. This is after i closed my case with Adobe and notified others that the web module was fixed in 4.1.
I give up and am going back to using 3.6 for a while!
Sorry to hear that! Had the same problem in 3.6 so going back is not a solution for me. However have in the meantime found that I only have the problem if I have both side panels open in the web module open. If I close one of the side panels while the system is stuck the process of opening the preview starts again.