Here is what I have done.
I've created an InfoPath 2010 form that allows the user to enter or select from a drop down lists a number that represents a Task ID. If data associated with the ID form one list matches data found in anothe rlist, information is returned. This is what it does and it works.
Publishng the form:
I went to Form Options > Compatibility > Form Type and selected Web Brownser Form
After I published to the Forms Library I went to Library Settings > Advanced > Opening Documents in the Browser and select Open in the Browser radio button.
When I access the site from a system that doesn't have InfoPath 2007 or 2010 and select the form I get "The form cannot be opened in a Web browser. To open the form, use Microsoft InfoPath.
What am I missing?
Thanks