Had the same problem with my Dell Dimension XPS T500 with a NVidia Viper TNT card.
Switching from a generic to a 386 kernel was not on itself the solution. ( Thought the legacy driver was only available in 386 format)
Added :
Option "ConnectedMonitor" "CRT"
to the Screen section as Jarle mentioned
Had the same problem with my Dell Dimension XPS T500 with a NVidia Viper TNT card.
Switching from a generic to a 386 kernel was not on itself the solution. ( Thought the legacy driver was only available in 386 format)
Added :
Option "ConnectedMonitor" "CRT"
to the Screen section as Jarle mentioned
=>
Problem solved !
Thanks Jarle