Bad page breaking in enumerations

["Duncan Hothersall" <dh@capdm.com>]

Hi all.

Have been having a very odd problem with some enumerations for a while. I
have the following standard preamble (relevant excerpt only):

---
%$Id: nubsmbabookbasic.tex,v 1.13 2001/08/08 11:02:19 dh Exp $
\setupoutput[pdftex]

%new enumeration commands
\defineenumeration[Activity]
	[text=Activity,
	before={\blank[2*big]},
	after={\blank[2*big]}]

\setupenumerations[Activity]
	[headstyle=\ss\tfa]

\setupbackground
	[background=screen,
	corner=round,
	offset=6pt]

\setupinmargin
	[align=right,
	style=\tfx\setupinterlinespace]
---

And, for example, the following document fragment:

---
This is a paragraph in running text.

\startsubactivity%
\margintext{\nohyphens\ss\bf This is the sidebar}
\startbackground
{\ss\sl This is the text of the activity telling you what to do ...

}\stopbackground

\stopsubactivity
This is another paragraph in running text.
---

I often get a page break between the "Activity X.X" title and the text of
the activity, even if there is practically a whole page free and the content
is no more than a few lines.

I assume it's something to do with the background, but can anyone tell me
how to phrase this better without the page breaking thing going on?

Thanks a lot.

Duncan

PS I know there is some funny spacing in the input sample - that is because
this stuff is generated from SGML/XML, and I wanted to give you exactly what
was going in, in case it was the white space that could be causing the
problem!