That's because those numbers are based on two small UK studies from the early 90's that were published by Goldberg et al in BMJ. When the numbers are small, the odds ratios can really throw off the "stats" that people will quote!1 in 500 seems wildly high to me, especially given the number of babies that are given that shot every day.
They were both small retrospective studies looking at kids with cancer - the first was only 33 cases, and the second was around 150 cases. Retrospective studies are not necessarily your "gold standard" when it comes to proving correlations.
Since then, there have been two large retrospective studies in the US and Sweden - both did NOT confirm Goldberg's findings. There was also a large case control study (better for figuring out correlations) that did not confirm the findings, and a "meta" study that combined the results of 6 case control studies that didn't confirm the findings.
This paper talks about the past studies, and has links to in the references to each. You have to click on the PMC free article link.
Vitamin K in neonates: facts and myths
Based on all that info, I personally don't believe that there is a link btw the two. Lilah had the Vit K shot, though our midwives gave us the option of the shot vs the oral suspension. I was too worried about remembering to give her the oral drops as it had to be done on a number of different occasions over baby's first few weeks of life (when I knew I'd probably be sleep-deprived and suffering from a case of baby brain! Haha