When I am in the DVD Prep & Burn Wizard and am going into the area were I should select a directory for preapared files the progress bar crashes at 90% (Subtitle & Menu Highlights - I think?).
Was there an error message? Based on where it crashed, it may have been an error about "complex menu / subtitle / highlights." A DVD has certain rules about how much information can be contained in subtitles and on menus. For example, if you have a lot of text links on a menu, setting them to Text Mask Overlay may be "too complex." Or if you have too much text on a single line of subtitles, it will be considered "too complex." Unfortunately, DVD 2.0 didn't tell you before the prepare stage that there was something wrong.
The 2.0a update fixes this (somewhat). Now, before you start preparing, DVDA will warn you that something is too complex. I haven't experiened this issue, but I don't think DVDA actually tells you which item is too complex or why (confirmation, someone?). But at least you get the chance to go back to find and fix it without having to wait for an aborted prepare.
I don't think anyone could really explain what to do to avoid this -- there's no "set limit" to how much text you can have on a line of subtitle, or how many text links you can have on a menu... it depends on what size font, how it's formated, maybe even what font is used?
Then again, maybe this isn't even what went wrong with yours. How much space have you got on the harddrive you're preparing to? And the drive being used for temp storage?