Thanks Spot for your very quick response. Yes I have checked any accidental changes such as nudging the opacity slider, and that no effects of any kind have been applied, yet Vegas still wants to do the full render. I have tested it over and over with sometimes just the one event.
There must be something going on but just can't think what it could be. Maybe it could be related to Vegas 4 still existing but I understand that the process of an upgrade still leaves the old version available, so still in the dark.

Just a few things to look for -

1> Project settings. Are your fields correct? Are all the files fields set correctly? A few times Vegas imported NTSC files with the incorrect field order, could do it for PAL as well. I never would have noticed except the same thing as you are asking about happened.

2> Correct output settings overall? 4:3 > 4:3? 16:9 > 16:9? Any conversion? 30i > 24p?

3> Just for the sake of it do you have any sort of cropping going on? 4:3 input files but outputting to 16:9? Or vice versa?

4> Did you add any velocity envelopes by mistake?

5> Do you have the option turned on to automaticly remove pull down in 24p files? I have found Vegas sometimes misreads files when this is turned on. I leave it turned off unless it is a 24p project.

Thank you filmy. I have gone carefully through all the things you listed and sadly the same issue remains.
At least I am very impressed with the genuine willingness of Vegas Users to help each other. I remain hopeful that the answer will come.

Post your VEG file somewhere and we'll take a look at it.

I run PAL and have V4 and V5 on the one system, no problemo here. Know that doesn't help much other than to prove it can work.
Bob.

Are you setting render quality to best ? That could do it.

The DV quality settings shouldn't be affecting unchanged video.

Did you capture this DV footage within Vegas or did you use a different capture application?

And - yes - as mentioned above - it would be very useful if you could share your project file so we could have a deeper look into it.

Marco

Thanks again everyone.
I will happily post the VEG file to look at, but not on my home computer right now, so will do this in next 8 hours or so.
To answer the questions raised:
Original video captured using Vegas
Various Render settings have been tried eg Good, Best

I have a wild theory that the program is behaving like a demo version (not so of course as I have registered it with Sony) because a message pops up every time telling me that over 80% of the project has to be rendered and do I wish to continue. I seem to recall that use to happen on a demo version I tried some time ago.

Thanks again everyone.
I will happily post the VEG file to look at, but not on my home computer right now, so will do this in next 8 hours or so.
To answer the questions raised:
Original video captured using Vegas
Various Render settings have been tried eg Good, Best

I have a wild theory that the program is behaving like a demo version (not so of course as I have registered it with Sony) because a message pops up every time telling me that over 80% of the project has to be rendered and do I wish to continue. I seem to recall that use to happen on a demo version I tried some time ago.

That message is merely confirming that Vegas truly believes it must need to render the entire timeline. The demo version does not have anything to do with this.

Try this....

Create a really simple Veg in V4 that uses these exact same source files. Just do a small test render. Verify that it renders as you would expect (actually by just doing a direct copy of the frames... very fast).

Save that Veg file.

Open that Veg file in V5. Render the file there to the exact same template settings you did in V4.

Make any difference?

If it is still not working as excpected then I would step away from the computer and ask for the help of someone versed in the techniques of exorsicm :-)

Failing that... posting that Veg file you have will allow others to verify again what may be going on.

Thanks Liam, I will try this when I get home tonight, and will post the result.