Lots of people would be willing to help, but don't know of a quick fix without more info about the kind of internal error.

If the internal error window is blank, you might be able to open Console (Utilities Folder) and look at the logs. With the console window open, try to open LW again, and the error message should be written to the Console window too. You can copy and post the first few key lines back here, and that will help.

(I'm guessing you did the usual safe boot/repair permissions after the update.)