Yes. As mentioned in my previous post - "smart-rendering" is a common feature of a lot of apps these days. No re-encoding is done just a stream copy. My favourite program for this is Womble - which you've already tried. So the issue has to be either the files themselves (you still haven't told us what the source is) or your setup.

At the bottom of the GSpot screen is a section labelled "Proposed Codec Solutions and Tests".

There will be some buttons labelled "1" "2" and "3" (the last two types probably greyed out to start with). Concentrate on the ones below GSpot "Vid" & "Aud" rather than "MS A/V" for the moment. Click on the "1" button for both the Video and Audio (one at a time) and check for any errors. Often one of the "2" buttons will then become enabled. Click on those, note any errors then the "3" and so on. Then try the "MS A/V" buttons.

The reason this is a useful exercise even if you think you've got a working system is often errors are hidden - something will fail but an alternative codec installation will be tried instead and may well partially work.

Often codecs and filters don't uninstall correctly and leave entries in the registry that "indicate" to other software that they can be used in filter chains for playing back or editing audio and video when in fact they are broken. Registry cleaners don't always pick these things up either.