If you see the following in Titanium:

[INFO] Compiling JavaScript...one moment
[INFO] No JavaScript errors detected.
[INFO] One moment, building ...
Traceback (most recent call last):
File "/Library/Application Support/Titanium/mobilesdk/osx/1.6.1/iphone/builder.py", line 1342, in 
main(sys.argv)
File "/Library/Application Support/Titanium/mobilesdk/osx/1.6.1/iphone/builder.py", line 505, in main
link_version = check_iphone_sdk(iphone_version)
File "/Library/Application Support/Titanium/mobilesdk/osx/1.6.1/iphone/builder.py", line 48, in check_iphone_sdk
output = run.run(["xcodebuild","-showsdks"],True,False)
File "/Library/Application Support/Titanium/mobilesdk/osx/1.6.1/iphone/run.py", line 7, in run
proc = subprocess.Popen(args, stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 595, in __init__
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 1106, in _execute_child
OSError: [Errno 2] No such file or directory

Double check the SDK field saying “loading.” If so, then you should go download “Xcode 4.02 and iOS SDK 4.3” or later.