If you have the iPhone SDKs installed on your machine, then do this:
- Open the iProxy Xcode project.
- Right click on iProxy in the Groups and Files panel on the left (the top most item) and select Get Info.
- Select All Configurations from the Configuration drop down.
- Select All Settings from the Show drop down.
- Under the Architectures heading, select iPhone Device 4.0 for the Base SDK setting.
- Do a Clean All.
- Compile and Run.
Also, there is an "iPhone OS Deployment Target" setting that should automatically change to "iPhone OS 4.0" when you set the Base SDK, but make sure that it actually got switched.
If you have any problems, let me know which step you're getting hung up on.