Copied from the Sony Vegas forum thread, "HDV users: please read", at  
http://www.sonycreativesoftware.com/forums/ShowMessage.asp?MessageID=602126&Replies=7
[I have added some notes - see below.]

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Subject: RE: HDV users: please read
Reply by: ForumAdmin Sony Creative Software Moderator
Date: 7/7/2008 3:32:22 PM
 
If you would like to help test the pre-release HDV reader for Vegas Pro 8, please
follow these exact steps:

1) Download the file "M2tsplug.zip" from this ftp site:
    ftp://md-ftp.sonycreativesoftware.com
    username: scsdev
    password: oh7e2McT

2) Unzip

3) Copy the file [SEE MY NOTE, BELOW - DR]
    "m2tsplug.dll" into (default path) C:\Program Files\Sony\Vegas Pro 8.0\FileIO
    Plug-Ins\m2tsplug . Choose yes when prompted to over-write.

4) Restart Vegas> Load up any HDV files or HDV projects you have been having
    trouble with. [SEE MY NOTE, BELOW - DR]

5) Please post your results back to this thread. Don't start another thread.

6) If you run into problems, please post details. Critical details are

a) full system specs

b) problem file genealogy

- What device recorded this file?
- Was the tape brand new, or was it used once or more?
- What application was used for capture?
- Has this file been opened or saved in ANY other application, such as Womble,
  or Premiere.
- What problem did you encounter (stability, red frames, black frames, other)

The more detail the better.
.......
Please limit your comments in this thread to HDV file problems only. This beta HDV
reader does not change the behavior of other source file types, it is for checking HDV
.m2t files only.

If you run into a problem with this new reader, please delete this file (m2tsplug.dll) and
un-install/ re-install Vegas Pro 8.0b. [SEE MY NOTE, BELOW, FOR "3" - DR]

Do not contact SCS tech support about this pre-release HDV reader for Vegas Pro 8.
This needs to be thought of as a component beta test between you, and SCS engineering.

Good luck, and we look forward to your results.

SCS dev

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NOTES - DR

3) To avoid having to reload Vegas if the new .dll file does not work correctly, *before*
    installing it, rename the current .dll as "m2tsplug.dll.old". You can (if you rename the new
    .dll "m2tsplug.dll.new") then swap the .dll files with careful renaming without needing to
    reload the program or to delete either .dll file (and you will not be prompted to overwrite 
    the old or new file).

4) This did not work for me (the project made with the old .dll file would never quite finish
    "building peaks" when opened with the new .dll installed). I needed to export the best 
    file I could with the old .dll installed, then open a new project with the new .dll and then 
    import the video file (the file should probably be run through Mpeg2repair first to check 
    for errors and to repair them before importing it).

  Back To HDV-Editing Page, Further Comments on VP-8