multiplying bands in gel purification

[John G. Luz]

Folks--I'm tearing my hair out.  I cut a nice clean tight band out of a
gel, and purified it with the qiagen gel extraction kit.  But when I ran
the gel-purified band out on a gel to check my yield, I got two bands,
both about equimolar.  One band looked about the right size.  The other
looked about 1kb smaller.  The band I gel-purified was 5.4 kb and cut
with NdeI and Xho.  What's going on?--John