Hi,
Other examples does nothing - there is no errors on \setlayer but
I didn't see any effect - no text is visible ;(
what version do you run?
pdfeTeX, Version 3.141592-1.11a-2.1 (MiKTeX 2.3)
ConTeXt ver: 2003.8.21 fmt: 2003.9.8
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Best regards
Martin