InfoPath Dev

I designed a product information InfoPath form. This form has a drop-down list box and several read-only text box. When a product code is chosen in drop-down list, the next text boxes will show related product parameters. This drop-down list box is binded to about 350 rows data in a SharePoint list. I can preview and select data rows in InfoPath design mode. But I cannot open it after published to SharePoint form library. It will take more than 10 minutes to load the form. Please help me, thank you!

 It really shouldn't take 10 minutes to load the form. Is that the only data connection? Is there other logic that may be going awry? Can you create a test form that just has a data connection to that same list and see if it also takes 10 minutes to load in the browser?