I had this same problem in NeroVision Express 3 (NVE) with the error message:
Unable to prepare data for recording: Failed to get disc content
I got the error several minutes after starting to burn a DVD movie that was based on three AVI files that I had captured from my DV camcorder. After much investigation I determined that the problem was that one of the AVI files was corrupted about halfway through. Apparently NVE3 choked on file (when it got to the corrupted part) and then NVE provided the aforementioned (unhelpful) error message. I suppose that NVE might give this same error message when it encounters any kind of corrupted audio or video file, like MPG, AVI, WMV, MP3, etc.
You can solve the problem by either recapturing the video file (hopefully uncorrupted), or by running a video repair tool on the video file. There are several video fix tools available for free, such as DivFix. There are several such tools listed on videohelp.com website.