Hi Hans,
Since a few weeks (or months?…) ago the use of \eqno and \eqalignno has been
changed in mkiv.
It is better to use the construction such as:
\placeformula
\startformula
\startalign
\NC H(I,J) \NC = H(I) + H(J|I) \NR[eq:equivoc]
\NC W(I,J) \NC = H(J) - H(J|I) \NR[eq:wedinfo]
\stopalign
\
This code now fails where before contextbeta had no problems:
tex error > tex error on line 101 in file Info/waarneming.tex: !
Misplaced alignment tab character &
&
l.101 H(I,J) &
= H(I) + H(J|I)\qquad&\hbox{\ineq[eq:equivoc]}\cr
99 \placeformula\startformula
100