The 430 go into power save mode and switched itself off?
I bought a new 430ex MKII today and a "Strobies isync 4" set of wireless triggers. It all works well until I stop for longer than 20 seconds then when I fire off another shot the speedlite doesn't trigger.
I reckon you're right...thanks for that.
Set C.Fn-01 to 1 to disable auto power off.
is your 430 set to slave? i.e. is it blinking red while it waits for the signal?