So sorry Lisa. I can't offer any advice re IUI never having had it but I know a lot of girls in here have so they could probably help more.
It sure is a big let down when you get treatment delayed and even worse when you start something and get it cancelled. I can't make you feel better honey, but just know that you aren't alone in here and you are definately justified in feeling devistated.
Hope things go the way they should quickly so you can start again soon. I is good to know however, that your body is responding so well to the drugs and that they just need to adjust the levels so you can start again straight away. That bit is great news.
big hug from me.