asterisk users - Oct 2003 - "Starting simple switch"

Hi list,

	I have an asterisk box with 8 zap channels (E400P, only one span, E&M
siginaling). And sometimes on the console, these messages apear about
some channels:

	-- Starting simple switch on 'Zap/4-1'	
	-- Starting simple switch on 'Zap/5-1'

And then:
	
	-- Hungup 'Zap/4-1'
	-- Hungup 'Zap/5-1'

	This ocurs with ramdom channels, sometimes all the channels. And
sometimes, when there is active calls, the calls hangs-up.
	
	Could anyone explain why it ocurs?

Thanks
Eduardo