Couple things to try (I always try the simplest fixes first):
- Try changing the input on the VCR
- Double-check connections to make sure secure and in right spots
- Hook the DVD player straight to TV and see if it works that way (Some copy protected DVDs don't like being run through recording devices.)
- Reset dvd player - maybe a setting got changed (Output set to DVI for example)
Hopefully one of those will fix, if not, comment back and we'll dig deeper.