Based on the fact that the selected aperture value of f/5 is at or near wide open for the 14-42mm f/3.5-5.6 at 32mm, we can eliminate the stuck aperture theory.

Based on your statement that it only ever seems to happen with one specific lens (but not the other lens that you regularly use), we can probably eliminate the stuck shutter theory (if the PEN E-PL1 even has a mechanical shutter).

That leaves some kind of weird interaction between a specific lens and the camera. Here are two things you can try to see if it helps:

• Look for any pieces of dust/debris that might be interfering with the connection between the lens' electrical contacts and the contacts on the camera.

• Examine the contact points on the lens and camera for excessive wear. Either the lens or the camera (but not usually both) will be spring loaded. Check for broken springs or springs that aren't pushing the contact all the way out as it should.

• Clean the contacts between the camera and lens with a soft dry cloth. Use dry or only with a drop or two of approved cleaning fluids applied to the cloth. Never apply any type of cleaning fluid directly to a camera or lens! Nikon recommends a general cleaning fluid such as surgical spirit applied to a lens cleaning tissue wrapped around a small wooden stick. Canon recommends a clean soft cloth. I could find no specific instructions regarding cleaning lens contacts from Olympus, but for the camera and lens in general the Pen E-PL1 Manual does generally warn against using "... strong solvents such as benzene or alcohol, or a chemically treated cloth."

• Be sure you are not pressing the lens release button when connecting a lens to the camera. The Olympus Pen E-PL1 Manual specifically warns that doing this can allow the lens to rotate past the proper alignment.