Building - Simulator/iPod oddness

Yesterday my (ContactMapper) app would not work on my iPod touch though it was fine in the simulator, except that the latter ignored any changes I made to the pin colour, always drawing it in purple.

Today I come back, run the app in the simulator and the pin is red! I change it to green. Build. Run – wow, the pin is green! I then select to build for the device. It builds, installs on my iPod touch and then drops a purple pin as the simulator had the day before! I touch all source files, rebuild and reinstall on my iPod and … the pin is still purple! I change the colour to red and rebuild for the simulator and I get a red pin. :-)

Can someone tell me what is going on here. Is there some improperly understood setting I need to change when I’m swapping between device targets to ensure it builds everything as I intend?

Xcode 3.2.2 and 3.1.3 SDK for Simulator/iPod