Many thanks, Steve.

Apologies - yes, HD here is High Def Video from a Sony Handycam tape played on the cam that recorded it in HD.

Yes, I'm using Vegas HD capture window with i-link/Firewire. I have the latest graphics driver but will check with Quick Time. (How come VLC Player has no problem playing the capture?)

>>>(How come VLC Player has no problem playing the capture?)<<<

A couple of tutorials on this forum here and here by musicvid10 might help understand.

Quoting from the latter one, if I may.
" 3) If the file opens in Vegas, or in Quicktime, or in Windows Media Player, or in Whatever Player, these programs will possibly provide some information about the CoDecs used to encode the file. Usually, this information is found in the "Media Properties" or "File Information" in these programs. Consult their respective "Help" files and functions for additional information."

Another piece of advice from the same source worth following:
"and only install a specific codec, if told to do so, from its manufacturer"

From the SCS Knowledgebase document #706 (updated 08/11/2014):
"If there are licensing issues with a certain format of video or audio stream, then we are not able to support that format. It is also possible that the format of one of the streams is something the software can support, but the codec was not included in the original software installation. If you install a third party codec that is able to process the file, you will likely be able to open and edit the media on the Vegas timeline."

Many thanks, vkmast. Happy to provide more about the captures if that helps with better diagnosis (I naively thought it might be an easy issue to sort).

The caps are from the Sony HDV Handycam HDR HC1E (PAL). With the MediaInfo tool you suggested, the spec from one of them reads:
.m2t extension
Container and general info:
MPEG-TS (HDV 1080i): 88.7MiB, 28s 400ms
overall bit rate mode: variable
overall bit rate: 26.1Mbps
maximum overall bit rate: 33Mbps
1 video stream: MPEG video
1 audio stream: MPEG audio

First video stream:
24.5Mbps, 1440*1080 (16.9), at 25.000 fps, MPEG video (Component) (Version 2) (Main@High 1440) (CustomMatrix / BVOP) (HDV 1080i)
First audio stream:
384 Kbps, 48.0 Khz, 2 channels, MPEG audio (Version 1)(Layer 2)

Look forward to hearing posters' suggestions as to why the video is not visible in Vegas 10, though the audio is audible, while VLC Media Player has no problem showing it.

Steve,
I'm now running the latest Quicktime version, but am still unable to see video in Vegas.

Thanks again for your help.

Can anyone throw any light on why Vegas can capture HD footage okay but cannot show the video stream when played back in the software, whereas VLC Player has no problem showing it correctly?

Also, an added complication. I tried to capture conventional DV footage from another camera's tapes, but upon selecting 'DV' from the Capture Video dialogue box, nothing further happened - no capture utility opened!

Could these two issues be connected?

I'm running Windows 8.1 - could that be the problem even though it's supposed to be compatible with Win8.1? Has anyone else successfully captured both DV and HD footage with Vegas Studio HD 10 from Windows 8.1?

All suggestions gratefully received.

Any help from here or here?
And pls tell us if you get a solution from the other forum?=)

Apologies for not being able to reply sooner. Many thanks for all the helpful posts. Here is the current state of play, which I hope will help anyone else in the same boat:

In desperation, I downloaded the trial version of Sony Vegas Platinum 13 and when I tried to launch the HDV capture function, it didn’t work – but with an error message that v10 did not display, saying that ‘MSVCR71.DLL could not be found’.

I searched online for solutions to this and found advice on doing a System File Check in the Run window so that Windows would automatically update files that had any issues. After doing it, the post said to reinstall the affected software, which I did and, lo and behold, the HDV and DV capture functions both worked correctly generating files with audio and video that played inside Vegas.

Thanks again for your help