hmm, it's a tricky one - but I don't think that the mod is actually causing the problem, rather is a symptom.
As far as I'm aware, ALL that the mod is doing, is calling a standard X-Cart button in the buy_now template. There is nothing else going on - simply it adds a button after the out of stock message, nothing more.
What you could try, is in your main.css - look for
.products .buy-now {
}
and change it to:
.products .buy-now {
- margin: 10px 0 0;
- width: 150px;
}
In otherwords, define a width to that box. You might want to adjust the value of the width.