Pre roll problem

Hi all,

We have the adtonomy’s player implemented in our page Formulatv.com, for instance in this url:http://www.formulatv.com/videos/1419/calista-flockhart-se-afeita-la-cabeza-en-cinco-hermanos/. This player uploads an adv. Pre-roll before showing the video. This pre roll is configured making a call to an ad server (Utarget) and this ad server gives back an XML with all the pre-roll’s parameters.
Our problem is that sometimes the player uploads the pre roll, and sometimes it doesn’t. Whenever we refresh the page or change from one video to another…
At first, we thought the problem was that the url gave back a blank call or a wrong XML, but it is not, it always gives back the right XML.
The problem is that the player sometimes uploads the pre roll and sometimes don’t.
We upload the pre roll with this parameter:
'http://www.utarget.co.uk/utpod/chooseAd.aspx?cid=1869&pick=true&impCount=true&of=adtonomy');

Could somebody help us, please?

Thanks in advance,

Francisco