SDL loses focus and never regains events

I’m not sure if this is a problem with KDE (3.2) or
X (XFree 4.2), or just me being a SDL noob:

I have an SDL app running in a window. When the app
is launched, SDL reports events. If I cause the SDL
window not to have focus, then give it focus again,
SDL doesn’t report any events.

Any thoughts or suggestions on what’s causing this?