The value of $y$ varies inversely as $\sqrt x$ and when $x=2$, $y=4$. What is $x$ when $y=1$?
Since $y$ and $\sqrt{x}$ are inversely proportional, this means that $y\sqrt{x}=k$ for some constant $k$.  Substituting the given values, when $x=2$ and $y=4$, we find that $4\sqrt{2}=k$.  Therefore, when $y=1$, we can solve for $x$: \begin{align*}
1\cdot\sqrt{x}&=4\sqrt{2}\\
\Rightarrow\qquad (\sqrt{x})^2&=(4\sqrt{2})^2\\
\Rightarrow\qquad x&=16\cdot2=\boxed{32}
\end{align*}