I'm facing this weird problem after a recent upgrade to Snow Leopard:

In about half of the cases I'm switching to application windows on a secondary/external display the mouse buttons and Macbook keyboard are unresponsive. I have to keep clicking/pressing for some time or have to switch between applications to get them working, until they'll fail again after some time.

I tested it with two different external displays with VGA and DVI adapter, different screen resolutions, I tested the mouse and mouse software, both keyboard and mouse work fine with the same applications moved to the primary laptop screen, trackpad works fine too.

This occurred after the upgrade to Snow Leopard on a 2008 unibody Macbook. Updates to 10.6.3 didn't solve the problem.

I'd be happy if anyone could help me with this issue.