Urgent index problem

[Duncan Hothersall <dh@capdm.com>]

I am one night from a deadline and I have just noticed that my index is 
silently ignoring some entries... Help!!

The following demonstrates the problem (tested on live.contextgarden.net):

--
\starttext
\startregister[index]{this term+in+particular} This term is discussed 
from the start of this page.\page[yes]
Some more text about the term, and another page.\page[yes]
And the end of the info about that term. \stopregister[index]{this 
term+in+particular}\page[yes]
A page unrelated to that term.\page[yes]
\index{this term+in+particular} And then another page on exactly the 
same term.\page[yes]
\placeindex\page[yes]
Disaster! The entry on page 5 has been eaten!
\stoptext
--

So we have the same terms referenced as a span over pages 1 to 3, and as 
a single entry on page 5. But only the span appears, not the second 
entry! The .tuo file contains:

\registerentry{index}{t}
\registerentrya{index}{this term}
\registerentryb{index}{in}
\registerentryc{index}{particular}
\registerfrom{index}{,}{1}{2::0:0:0:0:0:0:0::1}{1}
\registerpage{index}{,}{3}{2::0:0:0:0:0:0:0::5}{5}
\registerto{index}{,}{2}{2::0:0:0:0:0:0:0::3}{3}

so it looks like the sorting of these by page numbers has broken, and 
ConTeXt thinks that page 5 is between pages 1 and 3.

I hope someone can help...

Duncan