If you have following setup...
- You need to create InfoPath Form that you're going to use in Forms Server (=Browser compatible)
- Your form contains external data source to SharePoint list
- Data from the list needs to be in certain order in your form (in drop-down list box)
...you'll have issue because your items will be sorted in the order which they have been created. Underlying reason for that is the fact that Forms Server uses SharePoint object model to retrieve the items. So if you need other sort criteria then I suggest you to create your own custom Web Service that then returns the list in correct order. This is actually good in architectural sense since this gives you extra layer for business logic. And I really recommend you do that. See my previous posts for more information: From InfoPath to Database via Web Service and Adding own custom web service to SharePoint.
Anyways... Happy hacking!