Cant get rid of 2kb contaminant band during cloning

[rpandy2000 at yahoo.com]

clone has a 5kb insert in a 4kb vector. After mini/midi preps, however only a weak band at 9kb 
observed.Major band is a 2kb one on 1% agarose gel. gel isolated 9kb band, transformed and 
regrew up cultures...2kb band shows up again...restriction digests do not cut 2kb band but does 
cut 9kb band. sequencing indicates presence of complete insert in the DNA prep...HELP 

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