Hi Hans,

It seems that with the latest beta mkiv, version

	ConTeXt  ver: 2014.01.23 01:55 MKIV beta  fmt: 2014.1.23  

\widetilde and \widehat in mathmode are misplaced (and this is so in any of the fonts I tried).
Please compare the result of the following in mkii (where everything is correct) and in mkiv:
%%%% begin tilde-hat.tex
\starttext

We set ${\widetilde n}(t) := n(1 - t)$, and ${\widehat u}(\xi) := \int_{{\Bbb R}}\exp(-{\rm i}x\xi)f(x)dx$.

\stoptext
%%%% end tilde-hat.tex
The attached PDF is obtained with mkiv.
Best regards: OK