V4 was so much more stable than V5. Every Time I open it I get unknown error messages. It locks up and crashes when playing large HDV files but that might be because I am under powered for what I am doing. I didn’t ketch the exact problem that you are having but I have had problems with rendering CRB MPEG Transport streams HDV. It would get up 3.99Gbs and freeze. I finally tried doing a clean install on another drive. no problem rendering but I couldn’t get magic built to install. another Idea for your problems, Try creating a fresh new preset for your MPEG rendering I have found this to work when for some unknown reason one of the presets decides it just isn’t going to render at all.
as for flicker I haven’t noticed a big problem with text in menus unless I compress it allot. I have had problems with flickering text within video. increasing the bit rate in Vegas seams to reduce it but it still shows up on a interlace TV but not so much on a progressive monitor and not at all on the computer. I have seen previews on Hollywood movie DVD’s do the same thing so I am assuming it is the DVD player and TV more than the software. non the less an anti flicker option does sound good. I mostly render 24p and 30p DVD files which look great on an HD monitor but not as good on a standard TV set.