I had this problem and want to share just incase there is someone that has the same problem.
Error: "LU1875 This update failed during its preprocessing welcome text phase"

Solution.

Unregister and Re-register Navlucbk.dll file.

Here is a simple way to do. Follow these instructions:

1. Unregister Navlucbk.dll (C:\program files\norton antivirus\navlucbk.dll)
To unregister
a. Click Start > Run
b. In the Run dialogue box type or paste:
regsvr32 /u "c:\program files\norton antivirus\navlucbk.dll

2. Reregister
a. Click Start > Run
b. In the Run dialogue box type or paste
regsvr32 "c:\program files\norton antivirus\navlucbk.dll

3. Perform a disk Cleanup
4. Restart the Computer
5. Run liveupdate again

This post has been edited by zenix: Jul 31 2006, 11:27 PM