Try to hook up the VCR to work through channel 3/4 (switch on the back
for the internal rf-modulator) or 0 ("video", etc.),
depending on your setup. Try this setup (if you haven't already):

Cable-in to VCR RF in ("cable"; "antennae";
etc...)
VCR RF-out to TV ("out to TV")
VCR A/V in from DVD (use digital inputs of VCR to process DVD signal)

The VCR's in-board block-converter will be able to automatically
manage the two different inputs through the tuner. Often digital
input is referred to "channel 0" on the VCR tuner like an
additional channel, depending on model. Consult a manual for your
unit.

Be sure that if you use any one channel to view from the VCR, that the
channel is properly-tuned, and that if setup on channel 3, that both
are set to channel 3 or channel 4 respectively. This sounds like an
Automatic Fine Tuning conflict. An untuned channel will often go into
a seek-mode with most modern tuners, hence the V-sync mismatch,
because it cannot get a proper lock on the signal. The easiest
starting point is to try retuning your VCR tuner to what signal you
have available, then tune the TV to the VCR's signal.

If the above setup did not change matters, double-check that your TV
is set to CATV and not AIR. If your VCR/TV does not have an RF
output, you simply need an RF modulator.

I know exactly the problem you are describing and if I remember
correctly, it is solely with the signal tuning. This is not
indicative of a component problem with either the TV or the VCR. Set
AFT to on for both TV and VCR (where applicable) after tuning each in
the order specified above. Use channel 3 as a default for any input,
use channel 4 if channel 3 doesn't work. Make sure ch3-4 settings
match between all related tuners if such a setting exists (look on
the back of the units near where the RF cable connects for any kind
of switch).

Please post if the above does not work...