Why don't mlv files open after copying?

[Alex3000]

I shoot at 5dm2 on a fast 32GB card, I can't transfer the whole thing to a PC, it just freezes. One file is copied normally, but if you take, say, 7 and immediately transfer it, then it opens in mlvapp just a black screen, sometimes it says files not found. With what it can be connected?

[Walter Schulz]

Guesswork: Dying card or - more likely - cardreader going south.

[Skinny]

You can also try another USB cable with your cardreader if it has one.. I tried a few before I found the one that worked better.

[Kharak]

I had a sandisk card reader fail.

It could not finish transfers and therefore I had same issue with mlv files.

Try adifferent card reader.