I have the same problem on a very powerful PC. Try this: render your Panoramas step by step with 2, 4, 6, 8, 10, ….. images and detect the point the problem begins. I have no problems up to 10 images. But with 11 images LR gives me a message: Not enough Information about Camera-movement, panorama can`t be created. And with around 20 images LR renders infinitely.
And look at my other post:
Photoshop does the panorama rendering up to dozends of pictures without any problem. So I think the panorama engine in LR is still in its alpha stadium.
Meanwhile I have the same tests and jobs rendered with very small versions of the pictures (25% & JPEG instead of RAW files) and LR makes a mess, but no panorama. Some of the images are simply missing in the finished panorama.