You didn't give enough info to base advice on. There are several possibilities to explore.
What country do you live in?
Which model JVC?
Which type of media (-R, +R, -RW, +RW, DVD-RAM)?
Which brand of media?
Is this happening with different types and brands of blank disc, or have you only tried one?
Using the JVC tuner, or line inputs?
What are you trying to record? Off-air broadcast from an antenna, direct from cable wire, from satellite box, from cable box? Are you trying to copy a VHS?