If the CD has been written at high speed or to cheap crappy CDR's then you will not be able to get the missing data back to be able to repair or fix it.
Put the VCD into your burner abd run Isobuster (from _www.isobuster.com), select the avseq01.dat file, right click and select "Extract but filter on M2F2 mpeg frames". This will recover as much as possible, then burn back as a vcd with Nero. You way try to edit out error bits using TMPGEnc's MPEg Tools/ Merge & Cut feature first though.