\placeformula and $$ doesn't work anymore

[Hubertus Schmidt <stonemonkey@web.de>]

Hi all,
for some weeks I need to tex formulas again and tried the way I used to do it:

\placeformula
$$
f(t)={1\over2\pi}\int_0^\infty e^{i(\omega t-kx)} dx
$$

It didn't work anymore?!? It doesn't place a number nor does it do the spacing
properly. It does work the "context" way using

\placeformula
\startformula
f(t)={1\over2\pi}\int_0^\infty e^{i(\omega t-kx)} dx
\stopformula

but to be honest that's quit a lot to type. "$$" is just nice and short and all
the old documents I wrote wont work anymore...
I run

This is pdfeTeX, Version 3.141592-1.30.4-2.2 (Web2C 7.5.5) (format=cont-en 2006.
12.4)  4 DEC 2006 21:46
...
ConTeXt  ver: 2006.11.29 09:55 MK II  fmt: 2006.12.4  int: english/english

I would be very glad for some hints. Many thanks in advance.

Hubertus