Getting xib file errors and waring about lack compatibility with OS versions < 3.0

Question

I have a project that has existed for quite a while, and I recently upgraded it to 4.0. Though it now throws out a bunch of warnings and an error similar to this:

{some xib setting} is not supported on iPhone OS versions prior to 3.0.

I have the Base SDK set to 4.0, and the deployment target set to 3.1, so why does XCode think it needs to care about "iPhone OS version prior to 3.0"? Is there a build setting I have set wrong that I'm not finding here?

Here is a screenshot of a handful of the warnings.

Answer 1

Ah... eventually I deduced that if you click the waring icon in the lower right corner of the outline window of the opened xib, it brings up a window where you can set the deployment target for that xib. Changing it from 2.1 to 3.1 fixed my issues.