Sorry it took a few hours before responding, but first things first (luckily old setup of mkii turned to be working still).

Pinpointed the origin of the error message to this call:
   \the\everysetuppublications
I will search a bit further, but perhaps Taco has already enough clues from this experiment. 
Something with processcomma?
By the way, could it be related to some other error I get in mkiv in processing a description? There in the log similarly something with parameterlists seems at hand:
! Use of \@@startdescription doesn't match its definition.
\doifnextoptionalelse ...\nextoptionalcommandyes {
                                                  #1}\def \nextoptionalcomma...
\setuptextrules ...odoubleargument \getparameters 
                                                  [\??tl ]

Back to bib: From inserted code from bibl-tra.mkiv:

\writestatus{HVDM-TESTING =============>}{\string\setuppublicationlist[numbering=short,refcommand=data]}
\unprotect
\def\dosetuppublications[#1]%
  {\getparameters[\??pb][\c!alternative=,#1]%
\writestatus{HVDM-TESTING =============>}{after \string\getparameters <1>}%
   \doifsomething\@@pbalternative
     {\readsysfile{bibl-\@@pbalternative.tex}
        {\showmessage\m!publications{6}{bibl-\@@pbalternative}}
        {\showmessage\m!publications{1}{bibl-\@@pbalternative}}%
      \let\@@pbalternative\empty}%
   \getparameters[\??pb][#1]% as bibl-* can have set things back
\writestatus{HVDM-TESTING =============>}{after \string\getparameters <2>}%
   \the\everysetuppublications
\writestatus{HVDM-TESTING =============>}{after \string\the\string\everysetuppublications}%
   \ignorespaces}
\protect
\usepublications [literature]
\setuppublications [alternative=apa]
\setuppublications [numbering=short,refcommand=data] % separate -- see doc p2

And in the log:

HVDM-TESTING =============>: after \getparameters<1>
publications    : loading formatting style from bibl-apa
(/Users/hans/Documents/TeX/context/beta/tex/texmf-context/tex/context/bib/bibl-apa.tex
HVDM-TESTING =============>: after \getparameters<1>
HVDM-TESTING =============>: after \getparameters<2>
HVDM-TESTING =============>: after \the\everysetuppublications
)
HVDM-TESTING =============>: after \getparameters<2>
HVDM-TESTING =============>: after \the\everysetuppublications
HVDM-TESTING =============>: after \getparameters<1>
HVDM-TESTING =============>: after \getparameters<2>
! Parameters must be numbered consecutively.
<to be read again> 
                   ##
<argument> \def \@@pbinumbercommand ####
                                        1{\bibgetvars \currentpublicationkey }
\p!compareprocessaction ...commalistelement {#3}#2
                                                  \expandafter \quitcommalis...
\next1 #1,->\p!doprocessaction {#1}
                                   \doprocesscommaitem 
<argument> ...bibgetvars \currentpublicationkey },
                                                   \v!bib =>\def \@@pbinumbe...
\processnextcommalist ...dodoprocesscommaitem #4#5
                                                  ,]\relax \global \advance ...
...
l.32 ...ications [numbering=short,refcommand=data]

On 22 mrt 2010, at 10:56, Hans Hagen wrote:

On 22-3-2010 10:51, Taco Hoekwater wrote:


Hans van der Meer wrote:
The following I didn't use for some time. Is it replaced or broken in mkiv?
Is there a quick fix? I must retypsetting something I need on short notice.

Perhaps the quickest fix is to downgrade your context release for a bit.

This looks like an expansion bug, but I have no idea what could have
changed nor when.

mayhe hans can track down what command is triggering it, probably some command in the bib databae file

Hans


Hans van der Meer