Originally posted by Tchn226 same thing with ... don't know the word...
The word you're looking for is (more than likely) aperture
Does the same happen with another lens (e.g. kit lens) ? If so, it will point to the camera; if not, it will point to the lens.
Looks like it measures with the aperture closed in which case the view in the viewfinder should also be very dark; is that the case? It will indicate that the aperture linkage between camera and lens is broken in some way.
The flashing will indicate that it can not get correct exposure and explains the underexposure. But why does it not go to 30 sec or so? Maybe because you're in P? What happens when you're in Av mode?
But the inconsistency does not make sense at all.
If it's the camera (see first test), get a quote for repair. It might just be a spring that came loose or broke and might be reasonable cheap to fix.