Why won't Eclipse remember my launch configuration?

Question

I am using Eclipse 3.6 Helios on Windows.

Lately, my Eclipse install has been behaving erratically when I attempt to run/debug programs. In the past, Eclipse launched my project with the most recently used configuration whenever I pressed (Ctrl)F11 while in an editor window for a file within the particular project.

I've set up a simple test project (for an Android app, but it's the same for a regular Java application) and set up the proper configuration, but each time I attempt to run/debug it, Eclipse asks me what kind of application this is, and I have to manually select a configuration from a list (which includes options such as "JavaScript," which do not apply to any of my projects).

What am I doing wrong?